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1. 46 2 Sound Level Meters e125 544eu sede ser ewe sede aE 48 3 Octave Band Analyzer 2 45cctoces bch outendceseeeee s 53 4 Noise Dosimeter ii csea dese waseeeteteeatesieeeaceis 56 IV INVESTIGATION GUIDELINES 02 0 0 0 eee 60 A Planning the Investigation 0 0 0 00 e eee eee 61 1 Searching Online for Industry Noise Statistics 61 2 Equipment Needed for Worksite Noise Evaluations 64 B Reviewing Employer Records 0 0 0 ce eee eee eee 64 1 Reviewing Audiograms 0 0 e eee eee eee ee 65 2 Extended Workshifts 3 2 20 eecheseeea gn eee ese fh S sees 66 3 Hearing Conservation Program 00 0 0 e eee eee 67 C Conducting the Walkaround Evaluation 68 1 Create a Noise Diagram Noise Mapping 68 D Follow Up Monitoring 2csc lt sntcidessnesdveds sodeiderane 70 V HAZARD ABATEMENT AND CONTROL 70 A Engineering COMPOS 55 ccue say se cease on eeeeete xe ounce deans 70 1 Sourf e Tr atm nt 2 0 264adeeuee side see oueededeeseee ss 71 2 Path Treatment neuuueuununnua arurae 79 3 Receiver Treatment 14 2 oade vue feaedekdacweten oon ed oaks 89 B Engineering Controls and Economic Feasibility 90 l SOVEIMIOW s ercrcson cepi irka ti badia RERE EA bees Geseue es 90 2 Engineering Control Case Studies 04 90 Section II Cha
2. Advantages e Can provide 20 to 40 dB of noise reduction e Can be installed in a relatively short time frame e Can be purchased and installed at a reasonable cost e Provides significant noise reduction across a wide range of frequencies Disadvantages e Worker visual and physical access to equipment is restricted e Repeated disassembly and reassembly of the enclosure often results in the creation of significant sound flanking paths via small gaps and openings along the panel joints e Heat buildup inside the enclosure can be problematic e Internal lighting and fire suppression may need to be incorporated into the design e The long term potential for internal surface contamination from oil mist or other airborne particulates is high e The panels become damaged or the internal absorption material simply deteriorates over time e Enclosures require periodic maintenance such as replacement of seals and gasket material to keep the acoustical integrity at a high attenuation value Enclosures both off the shelf and custom design are available from a number of manufacturers listed in the Noise and Vibration Control Product Manufacturer Guide It can also be more cost effective to build enclosures in house by following the Guidelines for Building Enclosures Section III Chapter 5 Page 41 Acoustical Barriers An acoustical barrier is a partial partition inserted between the noise source and receiver which helps block
3. The cost of achieving acceptable noise levels varies greatly depending on the industry Even within specific industries noise levels can vary widely with different processes practices and equipment When a facility does make changes that include engineering control measures in a noisy area it rarely follows up with a detailed noise evaluation that documents the changes costs and extent to which noise decreased As a result published literature contains relatively few specific examples comparing the costs and benefits of engineering controls The economic feasibility of lowering noise levels with engineering controls is an important factor in deciding whether to implement specific controls In addition to the direct costs of design materials construction or installation and maintenance of engineering controls these controls can have indirect costs and benefits such as decreasing worker absenteeism increasing or decreasing worker productivity and increasing or decreasing the life of process equipment Furthermore if an engineering control reduces worker TWAs below 85 dBA the need for a hearing conservation program is eliminated along with the associated costs These costs include expenses for audiometry training HPDs recordkeeping and program administration As a general rule engineering controls increase in cost as their implementation moves further from the design stage It is typically cheaper to control noise by designing it ou
4. 2 Assumptions for an Economic Analysis To perform an economic analysis efficiently and realistically several assumptions need to be made Assumption 1 If actual life expectancy of equipment is known to the CSHO then it should be used If unknown assume the life expectancy of durable equipment engineering noise control is 10 years Regardless of the source of the life expectancy figure use it to determine the average cost per year i e total lump sum upfront costs for equipment divided by years of life expectancy Assumption 2 If actual costs for an engineering control are known to the CSHO then they should be used If costs for an item listed in Table V 6 are unknown the average cost in Table V 6 shall be used for cost estimating Assumption 3 The maintenance cost for an engineering control shall not exceed 5 of the initial cost per year over a 10 year time span based on guidance from the Office of the President of the United States OMB Assumption 4 If actual maintenance costs for an engineering control are known to the CSHO then they should be used If unknown then the percentage given in Table V 6 shall be used for cost estimating Assumption 5 The least expensive control option or group of controls that will achieve a reduction of 3 dBA or more in worker exposure shall be used for determining economic feasibility Assumption 6 An engineering or administrative control is economically feasible if its total cost
5. 23 Has the company made any effort to reduce noise levels 24 What is your opinion of the practicality of control measures 3 If noise screening results indicate elevated noise levels e g 80 dBA or above be prepared to sample on the day of the opening Develop a noise sampling strategy based on screening results and worker interviews Note It s amazing how many machines tend to go out of service when a facility knows that you are returning to do sampling Typically you can get 6 hours which is often sufficient to support a citation However if a return trip is necessary the CSHO will notify the employer that he she will need to set up full shift sampling for another day to assess the noise levels at the facility Look at dosimeter readings If you have an overexposure make sure it is well documented However if the projected dose exceeds or was close to the PEL and sampling time was inadequate then return for full shift sampling If the projected dose was well below the PEL and AL then the complaint was addressed in a defensible fashion and sampling can end if no other hazards are observed 4 Indicate to the employer how many workers you would like to sample and in what areas of the facility this will permit them to make appropriate arrangements 5 Schedule a date to return to the facility for full shift sampling Note Make sure that it s a typical exposure day representative of the routine high noise levels that you re
6. Chapter 5 Page 119 Where T is the permissible duration in hours and L is the measured sound level in dBA A worker s daily noise exposure typically comes from multiple sources which have different noise levels for different durations When adding different noise levels from various noise sources only noise levels exceeding 80 dBA should be considered The combined effect of these noise sources can be estimated using the following equation Sum C T Co T2 C3 T3 C Th Where C is the total duration of exposure at a specific noise level and T is the total duration of noise permitted at that decibel level If the sum equals or exceeds 1 the combined noise level is greater than the allowable level If the sum is less than 1 the combined noise level is less than the allowable level Example A worker in a machine shop is exposed to 95 dBA for 2 hours 69 to 78 dBA for 4 hours including a 15 minute break and 45 minute lunch and 90 dBA for 3 additional hours Example Worker s Activity Measured Sound Level Milling machine 6 00 a m 8 00 a m 95 dBA Peo ee a m 8 15 a m 69 dBA Parts department 8 15 a m 11 15 a m 78 dBA Lunch 11 15 a m 12 00 noon 69 dBA in break room 45 min Milling assist 12 00 noon 3 00 p m 90 dBA To determine if the worker s noise exposure exceeds a 90 dBA TWA use the previous equation Because the noise levels in the break room 69 dBA and parts department 78 dBA are below
7. 80 dBA these periods of the day are not included in the calculation According to the chart above workers are permitted to be exposed to 95 dBA for 4 hours per day and 90 dBA for 8 hours per day Calculate the ratio of actual exposure duration to permissible exposure duration for each time segment and add them 2 4 3 8 7 8 The resulting value 7 8 is less than 1 therefore this worker s exposure does not exceed the 90 dBA TWA However a separate calculation would be required to determine if a hearing conservation program is required B 5 Calculating the Equivalent A Weighted Sound Level La Occasionally it is necessary to convert a set of octave band sound pressure levels into an equivalent A weighted sound level This is easily done by applying the A scale correction factors for the nine standard octave center frequencies and combining the corrected values by decibel addition The A scale correction factors are the values of the A weighting network at the center of each particular octave band The value derived by combining the corrected values for each octave band is designated the A weighted sound level dBA Section III Chapter 5 Page 120 A Weighting Network of Sound Level Meters Relative Response dB 315 63 125 250 500 tk amp 4k 8k Octave Band Center Frequency Hz Example Octave Band Center Example L dB Pena Corrected Values Frequency Hz Bese dB Factor dB Look up on A weighted
8. A weighted 1 3 Octave Band SPLs dBA N o a 250 500 1 0K Frequency Hz Section III Chapter 5 Page 166 Pneumatic and Compressed Air Systems The 2 Step is to treat all open ended discharge lines and ports including standard air jets and nozzles with commercially available quiet design nozzles or pneumatic silencers Care must be exercised to ensure the type of device used meets the service needs at the plant Pneumatic and Compressed Air Systems There are two categories of devices 1 Air exhaust and 2 Service type devices Section III Chapter 5 Page 167 BENEFITS Rechsces the noise bevel 14 18 dBA Decreases air consumption 23 30 Satety nozzie Meets OSHA standards Courtesy of Silvent Inc WE Adjustable Air Nozzles Model 1009 and 1009SS Adjustable A Nozzles Adjustable Air Nozzles are suitable for a wide variety of blowoff applications The design allows you to tune in the force and flow to the application requirements thereby minimizing air consomption A micrometer bike dial indicates the gap setting A set screw in the end can be tightened 1o the air In amp SS O Courtesy of Exair Corporation Section III Chapter 5 Page 168 Pneumatic and Compressed Air Systems And there is an energy cost savings too For example blowing compressed air through a 10mm open pipe at a pressure of 5 bars uses 185 Nm hr At an average c
9. By sequentially switching the meter to each frequency band and taking a reading the CSHO can determine which octave bands are most represented in the noise For example an octave band analysis providing the following results indicated that the frequencies around 500 Hz and 1 000 Hz were most prominent Table III 1 Section HI Chapter 5 Page 54 Table III 1 Octave Band Analysis Noise A fiz pis fe ps fso S00 000 000 Jaooo eooo 16000 es foo m pe B fort pm In contrast the following octave band analysis Table II 2 obtained during concrete demolition multiple noise sources indicated that nearly all frequencies contributed to the noise level at that position a distance of 60 feet from the demolition point At that point the overall sound level was 91 dB demonstrating a standard principle of sound the sum of all octave bands is greater than any single octave band reading but the logarithmic values cannot be summed by simple arithmetic addition See Appendix B for more information on determining the sum of two or more sound levels Table III 2 Octave Band Analysis Noise B ss bo eos e e Figure 20 Octave Band Analyzer Graph 7 gt amp Some octave band analyzers can be set to automatic function i e the instrument automatically checks the sound level of each frequency band and stores the results Other instruments require the user to manually switch between the different frequency bands rec
10. Installation labor 2 workers x 12 hours x 27 hour 648 c Determine the total cost of engineering controls Add the cost of the mufflers acoustic absorbers barriers and installation 80 480 2 880 648 4 088 d Determine the cost of hearing conservation for all workers who would benefit from these controls Adjust the hearing conservation cost per worker Table V 5 and multiply that cost by the number of workers 12 12 workers x 2 shifts x 394 9 456 Given that the cost of engineering controls 4 088 is less than the cost of hearing conservation 9 456 these controls are both technically and economically feasible Inthe shakeout area full shift noise levels are 98 dBA to 100 dBA Four workers are employed here for each of two shifts Silica exposures for these workers are 3 to 4 times the PEL given that there is no local exhaust ventilation provided We propose a total enclosure of the shakeout that will be locally exhausted mechanically isolated from the shaker table and lined with some acoustically absorptive material This control approach if properly implemented will reduce the noise exposures to 90 dBA and the silica exposures to one quarter of the PEL Given that the daily noise levels do not exceed 100 dBA is enclosure of the shakeout economically feasible Because this engineering control will abate both silica and noise overexposures at the same time an economic analysis is not necessary T
11. Silencers Silencers are devices inserted in the path of a flowing medium such as a pipeline or duct to reduce the downstream sound level For industrial applications the medium typically is air There are basically four types of silencers dissipative absorptive reactive reflective combination of dissipative and reactive and pneumatic or compressed air devices This section will address the absorptive and reflective type a separate section will discuss the pneumatic or compressed air silencers The type of silencer required will depend on the spectral content of the noise source and operational conditions of the source itself Dissipative silencers use sound absorbing materials to surround or encompass the primary airflow passage These silencers principal method of sound attenuation is by absorption The advantages and disadvantages of dissipative silencers include Advantages e Very good medium frequency 500 2 000 Hz to high frequency gt 2 000 Hz attenuation e Low to medium pressure loss e They are a standard design Disadvantages e Poor low frequency lt 500 Hz attenuation e Very sensitive to moisture and particulates in the air stream e They can be a difficult retrofit Reactive silencers use sound reflections and large impedance changes area variations to reduce noise in the airflow The principal method of attenuation is through sound reflection which cancels and interferes with the oncoming sound waves The
12. The final two sections provide references used to produce this chapter and resources for obtaining additional information Following the main sections the appendices provide a glossary of terms sample calculations and expanded discussion of certain topics introduced in the chapter II Background Information A What Is Noise Occupational noise can be any sound in any work environment A textbook definition of sound is a rapid variation of atmospheric pressure caused by some disturbance of the air Sound propagates as a wave of positive pressure disturbances compressions and negative pressure disturbances rarefactions as shown in Figure 1 Sound can travel through any elastic medium e g air water wood metal Section III Chapter 5 Page 7 Figure 1 Sound Waves Areas of compression rarefaction and a sound wave co io RAREFACTION i LAA When air molecules are set to vibrate the ear perceives the variations in pressure as sound OTM Driscoll The vibrations are converted into mechanical energy by the middle ear subsequently moving microscopic hairs in the inner ear which in turn convert the sound waves into nerve impulses If the vibrations are too intense over time these microscopic hairs can be damaged causing hearing loss Noise is unwanted sound In the workplace sound that is intense enough to damage hearing is unwanted and therefore is considered to be noise Several key terms desc
13. e eee eee eee 110 H Associations Education and Conferences 000 110 LIST OF APPDENENDICES APPENDIX A GLOSSARY 0 0 00 cece eee eee 112 APPENDIX B SAMPLE EQUATIONS AND CALCULATIONS 118 APPENDIX C ULTRASOUND 22 02 2c e eee 124 APPENDIX D COMBINED EXPOSURE TO NOISE AND OTOTOXIC SUBSTANCES 0405 127 APPENDIX E NOISE REDUCTION RATING 00 133 APPENDIX F EVALUATING NOISE EXPOSURE OF WORKERS WEARING SOUND GENERATING HEADSETS 134 APPENDIX G ALTERNATIVES FOR EVALUATING BENEFITS AND COSTS OF NOISE CONTROL 136 Section II Chapter 5 Page 5 TABLE OF CONTENTS CONTINUED APPENDIX H JOB AID STEPS AND CHECKLISTS FOR CONDUCTING A NOISE INSPECTION 142 APPENDIX I JOB AID QUICK START QUEST NOISEPRO DOSIMETER INSTRUCTIONS 153 APPENDIX J REVIEWING AUDIOGRAMS 156 APPENDIX K THREE WAYS TO JUMP START A NOISE CONTROL PROGRAM 000 0000 ee 162 LIST OF TABLES Table J 1 Octave Band Filters and Frequency Range 14 Table II 2 Noise Measurements Exceeding the AL IMIS 1979 2006 23 Table l 3 Noise Measurements Exceeding the PEL IMIS 1979 2006 24 Table Il 4 Manufacturing Industry Noise Measurements Obtained Using AL Criteria IMIS 1979 2006 2 ee eee eee ee eee 24 Table Il 5 Manufacturing Industry Noise Measurements Obtained Using PEL Criteria IMIS 1979
14. with the dosimeter data Request copies of previous noise surveys or evaluations that included sound level measurements Note noise levels that exceed the AL along with the associated location equipment and activities Inquire about the duration of exposure and determine which workers might be exposed to the noise by using the equation for calculating the TWA for the percent dose see Appendix B Look at noise dosimetry data to determine whether workers were exposed over the AL or the PEL If the measurements are being used to show compliance check that the equipment used to make the measurements was at least a Type 2 sound level meter or dosimeter with periodic and daily calibration fully documented 1 Reviewing Audiograms Note In the early 1990 s Oregon OSHA adopted most of the Federal Noise standard with a few exceptions One exception was not allowing the use of presbycusis charts age correction factors when evaluating an employee s yearly hearing test to determine if a Standard Threshold Shift has occurred Oregon OSHA will allow the use of age correction charts only when determining that cases should be recorded on the OSHA 300 log see 8 4 2000 Interoffice Memorandum Look at the results of any audiometric evaluations Determine whether the audiometry was performed by a qualified individual using calibrated equipment and whether results of audiometric testing are compared to the worker s previous audiometric test resu
15. 000 workers who experienced significant loss of hearing due to workplace noise exposure Section II Chapter 5 Page 20 Figure 9 Distribution of Occupational Injury and Illness Cases Distribution of nonfatal occupational injury and illness cases by category of illness private industry 2010 Total cases 3 063 400 Skin diseases 15 8 Injuries 94 9 Other ilinesses 62 5 Injuries and ilinesses Illnesses Nonfatal occupational injuries accounted for the overwhelming majority of cases reported for the SOII in 2010 94 9 percent with illness accounting for the remaining 5 1 perfect of cases Most illness cases fall into the All other illnesses category which includes such things as repetitive motion cases and systemic diseases and disorders Source Bureau of Labor Statistics U S Department of Labor October 2011 3 Other Effects Other consequences of excessive workplace noise exposure include interference with communications and performance Workers might find it difficult to understand speech or auditory signals in areas with high noise levels Noisy environments also lead to a sense of isolation annoyance difficulty concentrating lowered morale reduced efficiency absenteeism and accidents As a general guideline the work area is too noisy if a worker cannot make himself understood without raising his or her voice while talking to a co worker 3 feet away In some individuals excessive noise exp
16. 17 D Hearing Loss To categorize different types of hearing loss the impairment is often described as either conductive or sensorineural or a combination of the two Conductive links to Noise eTool App I C 1 hearing loss results from any condition in the outer or middle ear that interferes with sound passing to the inner ear Excessive wax in the auditory canal a ruptured eardrum and other conditions of the outer or middle ear can produce conductive hearing loss Although work related conductive hearing loss is not common it can occur when an accident results in a head injury or penetration of the eardrum by a sharp object or by any event that ruptures the eardrum or breaks the ossicular chain formed by the small bones in the middle ear e g impulsive noise caused by explosives or firearms Conductive hearing loss may be reversible through medical or surgical treatment It is characterized by relatively uniformly reduced hearing across all frequencies in tests of the ear with no reduction during hearing tests that transmit sound through bone conduction Sensorineural links to Noise eTool App I C 2 hearing loss is a permanent condition that usually cannot be treated medically or surgically and is associated with irreversible damage to the inner ear The normal aging process and excessive noise exposure are both notable causes of sensorineural hearing loss Studies show that exposure to noise damages the sensory hair cells that line the
17. 2006 22 a sceaene es ce ces ceeeeeces sates 25 Table Il 6 Summary of Average TWA Construction Noise Exposure 27 Table Il 7 Task Specific Average Noise Levels by Construction Trade 27 Table I 11 Octave Band Analysis Noise A 00 02 eee 55 Table HI 2 Octave Band Analysis Noise B 0 0 ee eee 55 Table IV 1 Example Incidence Rates of Nonfatal Occupational Illness 62 Table IV 2 Inspection Statistics for SIC 2047 Dog and Cat Food Manufacturing in FY 2011 Organized by Most Frequently Cited 63 Sandar eee am Na OE Ur Om Dac Table V 3 Extended Workshifts and Action Level Reduction 66 Table V 1 Effect of Thickness on Sound Absorption Coefficients 81 Table V 2 Absorption Coefficients of Common Surface Materials and Finishes 2 4 44 e3 ie ee ee Reese cee pew eetadedeawen a a 81 Table V 3 Effect of Thickness on Transmission Loss Values for Plywood BNO Steel dB cu ie ciao en seta Ce Cel Gaeta ewes D 83 Table V 4 Relative Transmission Loss for Example Materials dB 83 Table V 5 Hearing Conservation Program Costs and Corrections Based on Worker Geography 2 3 25 lt 2 ee lt 4nd needtewsedeeereeerewrsoewaes 100 Table V 6 Noise Control Engineering Cost Assumptions 101 Section III Chapter 5 Page 6 The mention of trade names commercial products or organizations does not imply endorsement by Oregon OSHA or the U S Government I Introduction Noise
18. 94 5 dBA at its muffler A team of student researchers developed a way to construct an additional muffler to reduce the noise level to 75 5 dBA using common materials that cost less than 5 in total These materials included a Viton O ring PVC housing an 8 mm bolt and a hose plug C Economic Feasibility of Noise Control Engineering 1 Background This section suggests methods that CSHOs can use to evaluate the economic feasibility of noise engineering controls relative to current enforcement policy and for pre citation documentation purposes These methods are useful whenever the daily noise exposure exceeds the levels listed in 29 CFR 1910 95 and 20 CFR 1926 52 Note on Costs Dollar amounts quoted in this section are relative estimates used as examples to demonstrate methods for determining whether implementing a hearing conservation program or engineering controls is more economical Actual costs will vary based on factors such as location availability of supplies and varying cost inflation The CSHO should investigate local costs in situations where the relative cost differential is close as determined following this procedure The economic feasibility of noise engineering controls has been calculated using several different methods over the past decade The primary difference between the methods involves how the costs of noise exposure are calculated i e to what extent calculations include potential disability claims work
19. A a Section III Chapter 5 Page 23 Table II 3 Noise Measurements Exceeding the PEL IMIS 1979 2006 Table Il 4 Manufacturing Industry Noise Measurements Obtained Using AL Criteria IMIS 1979 2006 Median Over the NAICS NAICS Title Total Records dBA AL 335 Electrical Equipment Appliance and Component 2 679 85 84 57 Manufacturing 336 Transportation Equipment Manufacturing 5 660 87 38 67 337 Furniture and Related Product Manufacturing 3 867 86 83 64 339 Miscellaneous Manufacturing 2 156 85 62 55 Section III Chapter 5 Page 24 Table H 5 Manufacturing Industry Noise Measurements Obtained Using PEL Criteria IMIS 1979 2006 Total Median Over Noise Measurements NAICS NAICS Title Records dBA the PEL in dB Range 100 to 90 to 94 95 to 100 104 105 dB dBA dBA EN Beverage and Tobacco 85 64 25 25 Product Manufacturing 314 Textile Product Mills 2 a 89 40 Apparel Manufacturing 828 81 32 Leather and Allied 89 71 48 35 EN 1 Product Manufacturing Wood Product 16 330 91 72 60 30 22 Manufacturing E Paper Manufacturing 4 344 87 90 ae ae Printing and Related 2 620 82 22 17 15 Support Activities Petroleum and Coal 86 72 27 22 Products Manufacturing zee Chemical Manufacturing 2 611 85 20 KIE REA Plastics and Rubber 7 627 86 07 30 21 Products Manufacturing Nonmetallic Mineral 5 772 88 39 41 26 10 Product Manufacturing 331 Primary Metal 13 196 91 32 58 34 19 5 1 Manufa
20. ANST Standard 1 4 1971 R1976 or S1 4 1983 Specifications for Sound Level Meters These ANSI standards set performance and accuracy tolerances according to three levels of precision Types 0 1 and 2 e Type 0 is used in laboratories e Type is used for precision measurements in the field e Type 2 is used for general purpose measurements The most widely used sound level meter for workplace evaluations the Type 2 meter performs with the minimum level of precision required by Oregon OSHA for noise measurements These meters are usually sufficient for general purpose noise surveys For compliance purposes readings obtained with a Type 2 sound level meter are considered to have an accuracy of dBA One model of sound level meter typically used by CSHOs the 3MSoundPro is designed to operate in temperatures of 14 to 122 F 10 C to 50 C Over this range temperature has a modest effect on the accuracy of measurements less than 0 5 dB Likewise the sound level meter can be expected to operate effectively between 10 and 90 relative humidity In contrast a Type 1 meter has an accuracy of 1 dBA The Type 1 meter accuracy precision and additional features make it the preferred model for obtaining readings that will be used to help design cost effective noise controls Section III Chapter 5 Page 49 For unusual measurement situations refer to the manufacturer s instructions and appropriate ANSI standards for gu
21. Manufacturer Guide should be consulted for a partial list of the manufacturers of these products and applications Specific retrofit materials and or applications include the following Vibration Damping Vibration damping materials are an effective retrofit for controlling resonant tones radiated by vibrating metal panels or surface areas In addition this application can minimize the transfer of high frequency sound energy through a panel The two basic damping applications are free layer and constrained layer damping Free layer damping also known as extensional damping consists of attaching an energy dissipating material on one or both sides of a relatively thin metal panel As a guide free layer damping works best on panels less than 4 inch thick For thicker machine casings or structures the best application is constrained layer damping which consists of damping material bonded to the metal surface covered by an outer metal constraining layer forming a laminated construction Each application can provide up to 30 dB of noise reduction It is important to note that the noise reduction capabilities of the damping application are essentially equal regardless of which side it is applied to on a panel or structure Also for practical purposes it is not necessary to cover 100 of a panel to achieve a significant noise reduction For example 50 coverage of a surface area will provide a noise reduction that is roughly 3 dB less than 100 covera
22. Oregon OSHA Laboratory Section II Chapter 5 Page 47 if questions arise In general as long as the sound level readout is within 0 2 dB of the known source the calibrator output it is suggested that no calibration adjustments be made If large fluctuations greater than 1 dB in the level occur then either the calibrator or the instrument may have a problem Review your noise instrument calibration procedure and check whether your process 1 Confirms that both the calibrator and the instrument have not exceeded the periodic calibration due date 2 Uses the correct calibrator for the instrument 3 Uses the correct adaptor between the calibrator and the instrument microphone 4 Confirms the battery charge 5 Adjusts the instrument calibration when the tolerance is within the manufacturer s published limits e g 0 2 to 1dB but rejects the equipment if the calibration reading is outside the limits e g 1 dB or more 6 Prevents use of equipment that is outside its periodic calibration due date or fails pre use calibration 7 Creates a record of pre use calibration Additionally confirm that you know how to change the battery in both the calibrator and the instruments If in doubt review instructions in each instrument s user s manual A low battery is the number one cause of equipment failing pre and post use calibration Changing the battery will often bring the equipment back into an acceptable calibration rang
23. Table G 16A is the exposure duration for a specified TWA sound level at which a dose of 100 will occur Also the PEL is not reduced for extended workshifts PEL compliance is measured using a dosimeter set with a threshold of 90 dBA any noise below 90 dBA is not integrated into the dose measurement Section III Chapter 5 Page 66 Extended Workshifts Standard Interpretation OSHA 1982 Extended workshifts do not affect the PEL but do affect the Action Level AL using the following equation AL 16 61 logio 50 12 5 hours 90 For example workers exposed to a noise over a 10 hour workshift will have the following AL ALjo 16 61 logio 50 12 5 10 90 83 4 dBA For compliance purposes reading with a Type 2 soundlevel meter and dosimeter are considered to have an accuracy of 2 dBA Therefore the adjusted AL o 83 4 2 85 4 dBA If a worker works an 8 hour shift and has a noise exposure of 85 7 dBA as an 8 hour TWA there is no violation This is because the measured noise exposure does not exceed the adjusted AL of 87 dBA 85 dBA 2 dBA allowed for Type 2 meter accuracy Extended Workshifts Another Sample Calculation Given e 9 5 hour workshift e Employee noise dose was 53 during a 460 minute sample ALo5 16 61 logio 50 12 5 9 5 90 83 8 dBA Adjusted AL 83 8 2 meter accuracy 85 8 dBA Employee Exposure TWA 16 61 logio 53 100 90 85 4 dBA For more information
24. VA American Industrial Hygiene Association Barron R F 2003 Industrial Noise Control and Acoustics New York NY Marcel Dekker Inc Bell L H and D H Bell 1994 Industrial Noise Control Fundamentals and Application 2nd edition New York NY Marcel Dekker Inc Bruce R D A S Bommer and C T Moritz 2003 Noise Vibration and Ultrasound In The Occupational Environment Its Evaluation Control and Management Second Edition Fairfax Virginia American Industrial Hygiene Association Pages 435 475 Bureau of Labor Statistics 2009 Occupational employment and wages 49 9043 maintenance workers machinery May Bureau of Labor Statistics 2009b Employer costs for employee compensation June Centers for Disease Control 1996 National Institute for Occupational Safety and Health Preventing Occupational Hearing Loss A Practical Guide Eds John R Franks Mark R Stephenson and Carol J Merry NIOSH Cox T J and P D Antonio 2004 Acoustic absorbers and diffusers theory design and application New York NY Spon Press Appendix A Driscoll D P and L H Royster 2003 Chapter 9 Noise Control Engineering In American Industrial Hygiene Association The Noise Manual 5th edition Edited by E H Berger et al Fairfax VA American Industrial Hygiene Association Driscoll Dennis P 2011 The Economics of Noise Control Engineering Versus the Hearing Conservation Program Associates in Acoustics Inc October
25. Who determines which hearing loss cases are recorded This job aid is intended to provide CSHOs with a nonmandatory approach to conducting noise inspections CSHOs may use this job aid may modify the job aid or may use any approach they feel is the most appropriate for the inspection This job aid does not set any new OSHA policies or requirements Section III Chapter 5 Page 152 APPENDIX I Job Aid Quick Start Quest Noisepro Dosimeter Instructions Turn On 1 Reset Turn on unit by pressing and releasing On Off ESC key The display will initialize and sequence to the START screen If LOBAT is in display put fresh batteries in the unit Press and hold RESET soft key the display counts down from 5 and indicates Deleting All Studies on display A solid box icon in lower right corner of the display means data has been erased from the unit NOTE Resetting the unit erases all previously stored data from memory Verify Current Setup 4 From the START menu go to SETUP menu using the arrow A V keys and press key Press the corresponding soft key for DOSE1 An asterisk denotes the current active setup for the selected DOSIMETER DOSE should be set up for OSHA HC Press key to view the selected setup The selected setup menu offers the options to View Set Parameters View Set Range View Set Weighting and Save to Dosimeter 1 Use the A Y arrow keys to select the desired item In this example sel
26. a material that reflects 66 of the sound energy that reaches it will absorb the remaining 34 and have an absorption coefficient of 0 34 Materials that absorb sound particularly well such as fiberglass acoustical panels have absorption coefficients approaching 1 An absorption coefficient reported as greater than 1 is an artifact of the test conditions Table V 1 displays the sound absorption coefficients for three common sound absorbant materials The amount of noise absorbed by these materials depends on the density and thickness of the material and the frequency of the sound Driscoll Principles of Noise Control Section III Chapter 5 Page 80 Table V 1 Effect of Thickness on Sound Absorption Coefficients Random Incident Sound Absorption Coefficient with Solid Range of Backing 4 Mounting Volume Range of Density Thickness Thickness Density _Q ve Band Center Frequency Hz Material lb ft Inches Inches lb ft kepa aa n o 15 oalon 099 099 099 0 99 20 30 oz los2 099 0 99 0 99 099 Open cell acoustical 1 8 to 2 5 1 4 to 2 C eee foam Driscoll Room Acoustics V2 Frequency also influences sound absorption by materials Table V 2 shows the absorption coefficient for common building materials at different frequencies Note that dense materials such as rough concrete absorb lower frequencies better than other materials while high frequencies are better absorbed by less d
27. a measurable noise reduction the original room must be acoustically hard In other words the room surfaces must be made of highly reflective materials such as concrete or painted cinder block As well as the sound material used to absorb sound in a room or enclosure it is common to use sound isolating material also known as sound transmission loss material to block sound from propagating from one room to another or from inside an enclosure to outside Often as with enclosures and pipe insulation one desires a combination of absorptive and sound isolation qualities Unlike damping materials however it is critical for the sound absorption material to be directly exposed to the source or noise Attaching acoustical foam on the outside of a metal enclosure does not reduce noise the material needs to be on the inside surface areas This may sound simple but it is not uncommon to find materials improperly used in this manner Keep the function of each material in mind For the purpose of designing noise controls it is useful to be able to compare the characteristics of different materials The tendency of a material to absorb or reflect a sound is numerically represented by its absorption coefficient the ratio of sound energy absorbed by the material to the sound energy incident to striking the material s surface This coefficient is a decimal value between 0 all sound reflected and none absorbed and 1 all sound absorbed In simple terms
28. advantages and disadvantages of reactive silencers include Advantages e Good low frequency attenuation e Can be designed to minimize pure tones Section III Chapter 5 Page 36 e Can be used in high temperature and corrosive environments Disadvantages e Usually there is a high cost when fabricated from corrosion resistant materials e Sensitive to particulate and moisture contamination e Relatively narrow range of attenuation e High to medium pressure loss e They can be a difficult retrofit e They can be expensive because they are typically a custom design The combination dissipative and reactive silencer is essentially a reactive silencer with sound absorption added to provide high frequency attenuation capabilities The advantages and disadvantages are similar to those listed for each type To determine which type of silencer is best for a particular application a trained professional should be consulted The manufacturer or a designated representative will need to work closely with the facility engineering representative s to clearly identify all operational and physical constraints The Noise and Vibration Control Product Manufacturer Guide contains a partial list of silencer manufacturers and their websites Typical applications for silencers include e High pressure gas pressure regulators air vents and blow downs e Internal combustion engines e Reciprocating compressors e Centrifugal compressors e Ro
29. at the time of the baseline audiogram from their age at the time of the suspected threshold shift Subtract the difference in the age correction values from the difference between the current and baseline audiograms Take the average of the age corrected threshold shifts at the three required frequencies if the average is 10 dB or higher an STS has occurred See Appendix J for more information about adjusting audiograms for age 2 Extended Workshifts For workers working longer than an 8 hour shift the AL for hearing conservation is reduced proportionately from 85 dBA For the reduction equation see Appendix B Table IV 3 shows the AL 50 dose based on shift duration Table IV 3 Extended Workshifts and Action Level Reduction Exposure Time hours Action Level dBA 85 84 2 It is preferable to determine compliance with the reduced AL by performing dosimetry for as much of the shift as possible Perform full shift dosimetry whenever possible Use a dosimeter set to a 90 dBA PEL 80 dBA threshold 5 dB exchange rate and slow response CSHOs who use representative sound level meter readings instead of dosimetry to document exposures should ensure that such readings are taken as close to the hearing zone of the worker as possible and that the period of time represented by each segment of exposure is documented Table G 16A in Appendix A of 1910 95 lists the reference duration for various sound levels The reference duration in
30. better design criterion would be to limit sound levels to 60 dBA or less As mentioned above for a personnel enclosure to work well it is critical that worker s spend a significant portion of their workshift in the shelter The amount of time needed inside the enclosure will depend on the magnitude of the existing noise exposure Appendix A Noise Exposure Computation of the OSHA Occupational Noise Exposure standard 29 CFR 1910 95 can be used to help determine the amount of time needed inside an enclosure to reduce noise exposures below select target levels such as a TWA of 90 dBA or 85 dBA Relocation Finally if it is not essential for the worker to spend significant time in the immediate vicinity of noisy equipment then another option for reducing noise exposure would be to relocate the worker to a quieter area when practical Quite often equipment operators will spend most of their time up close to the production or process equipment when in fact they could stand back 5 to 7 feet where the sound level might be a few decibels less For relocation to work however it is critical that the worker still be able to perform the same job function To help identify areas or zones where lower noise levels exist a comprehensive sound survey of the production area is recommended It is also valuable to plot the sound level data on an equipment layout or floor plan then add or draw contour lines of equal sound levels This results in a noise c
31. cable underneath clothing to prevent it from catching on anything Press the RUN PAUSE key to begin data collection The run icon gt will appear in the lower right corner of the display While the test is running you can view current data on the display of the NoisePro End Study 13 14 Press RUN PAUSE key to stop study The pause icon U will appear in the lower right corner of the display Remove the microphone and NoisePro from the subject Tip It s best not to handle the microphone while the NoisePro is collecting data in Run mode Review Data 15 16 17 18 19 From the START screen highlight VIEW SESSION and press the key Press the various soft keys for AVG DOSE and SUMRY to obtain data and data summary In addition the arrow keys A V will scroll through SPL PEAK MAX MIN LAVG TWA PTWA DOSE PDOSE and RTIME Run Time information Use the lt P arrow keys to toggle between HC 1910 95 c and PEL 1910 95 b 1 data Note STUDIES are sound level measurements separated by paused periods that allow time for work breaks lunch period or to store measurements for separate evaluation i e different job tasks Studies are grouped together in a session A typical session consists of the recording of multiple studies in a work day VIEW SESSION will give you derived values based on results for all studies in the SESSION Example 1 A typical workshift you would start run the dosimet
32. ceiling This engineering control will do nothing to reduce the noise level from the noise source but will reduce the reflection of noise back into the room As was mentioned previously this type of control works best in a small room less than 10 000 square feet with low ceilings less than 15 feet In a room with high ceilings the main source of noise to which workers are exposed is most likely direct noise from the source Sound absorbing materials should never be painted as this would cover the pores in the material thereby preventing noise from being absorbed Figure 38 Sound Absorbing Baffles sound absorbing baffles sound absorbing panel on lowered frame Reflective and absorptive materials are able to reduce noise levels in different ways Engineered noise control laminates combine two or more layers of diverse materials with different properties often with an air space between them These layered materials absorb a high percentage of sound and then attenuate the sound to maximize the transmission loss The sound is effectively captured with minimal reflection and transmission Section III Chapter 5 Page 85 An alternate method of interrupting the noise path is to relocate the noise source For example air expansion at valves can cause significant noise these valves can be routed to an area away from the worker by extending the piping which would remove the noise source from the worker
33. consist of documenting the A weighted sound level at fixed locations for each machine or production line Section III Chapter 5 Page 174 Production Office RA SC gee TUUUUUHHUIUII Room 1L Example Noise Contour Map Acoustical Maintenance Periodically bi monthly quarterly or at least semi annually conduct a general sound survey of each machine and compare the operating sound level with the baseline sound level data If noise generating elements are identified or the sound levels indicate at least an increase over the baseline data of 2 dBA then appropriate repair should be performed and Section III Chapter 5 Page 175 Acoustical Maintenance Maintenance and operating personnel should be trained to observe and listen for potential noise sources outside the norm for the equipment of concern They should become familiar with the noise generating mechanisms of each machine and with the visual inspection procedures Acoustical Maintenance When a noise producing problem is identified during a visual and auditory inspection the problem should be corrected immediately if it involves only a minor malfunction or adjustment and even if the equipment appears to be operating normally If the problem requires more extensive attention then it should be labeled or tagged at the problem location and be scheduled for service during the next maintenance round Section III Chapter 5 Page 176 Ac
34. consult the damping material manufacturers to identify optimal materials Keep in mind that the machine the product being manufactured and the process itself can all create and radiate noise Consider the illustration in Figure 32 conveying rocks into a hopper In the example on the left side the rocks impacting the metal paneled walls of the hopper cause it to ring like a bell As shown on the right side reducing the free fall height by backing up the conveyor such that there is only a short drop significantly reduces the potential energy which reduces the resultant noise Additionally a durable rubber like material is added to damp the hopper and minimize the ability of the metal panel to flex and vibrate which eliminates this noise at the source Damping material can be added to either side of the metal surface Driscoll Principles of Noise Control Section III Chapter 5 Page 76 Figure 32 Reducing Free Fall Height Free Fall Height From Noise Control Principles and Practice Bruel amp Kjaer Driscoll Principles of Noise Control Damping materials are often used to reduce the response of a vibrating surface They work by dissipating the mechanical energy of a vibrating panel in a way that does not allow the energy to re radiate into the air as noise The mechanical energy from a vibrating surface is typically converted into heat in the damping material though the change in temperature is usually too smal
35. d1 d2 Where Lpaz is the sound pressure level at the new distance from the noise source L is the sound pressure level at the original distance d is the original distance and d2 is the new distance Example The sound pressure level of an aircraft engine in the middle of an open runway is 120 dBA at a distance of 50 ft from the receiver The sound pressure level at a distance of 80 ft is calculated using the equation above Lyq is 120 dBA d1 is 50 ft and d2 is 80 ft Therefore Lpa2 is 120 20 x log 50 80 which is 116 dBA B 7 Reducing the Action Level for Extended Workshifts If a worker works longer than an 8 hour shift the action level AL for hearing conservation is reduced proportionally from 85 dBA using the following equation Section III Chapter 5 Page 122 AL 16 61 50 logio 90 12 5 x hours worked Example A worker works a 10 75 hour shift in a car parts manufacturing plant What will be the worker s reduced AL AL 16 61 50 90 82 9 logio __ dBA 12 5 x 10 75 B 8 Converting a Single Dose Measurement to an 8 hour TWA Sound Level A dose measurement can be converted to an 8 hour TWA sound level using the following equation dose 90 TWA 16 61 logio 100 Where the dose is a percentage and the TWA is on an A weighted scale A factory hires a health and safety consultant to measure the noise exposure of the workers The consultant writes a report that states that workers are exposed to a 18
36. dosimeter is not turned off make sure there are no loud noises during lunch that can contribute to the noise dose e g radio turned high in car or lunchroom Once the 8 hour exposure is determined you should continue to allow the dosimeter to collect data to determine the severity e g continual noise exposure during last 2 hours of a 10 hour shift can increase severity of the citation based on full extended shift sampling e Complete all information on OSHA noise survey report f Post calibrate noise equipment and fully document calibration this is often done after leaving the site One could demonstrate a calculation where the CSHO allowed the dosimeter to accumulate for 8 5 hours e g not collecting it at lunch and not documenting the exposure during the lunch break and with significant noise in the first 5 minutes and last 5 minutes of the slightly extended workshift and never be over the 8 hour PEL This is the reason to take SLM measurements throughout the workshift to fully document noise fluctuations 5 Notify employer of noise sample results prior to leaving worksite and note the employer s opinion of practicality of control measures 6 Review relevant records e g hearing conservation program Section III Chapter 5 Page 149 7 Conduct additional interviews with employer and worker regarding employer s hearing conservation program and feasibility of engineering controls Request copies of manufac
37. in excess of 50 of the PEL 1 What is the cost of a hearing conservation program per worker for this foundry From Assumption 10 and Table V 5 we have 375 x 05 375 19 375 394 Therefore the cost of a hearing conservation program per worker at this foundry is 394 Note on Noise Evaluation Threshold This example Dusty Foundry can also be used to demonstrate another topic when different noise measurement thresholds are appropriate In this example the noise evaluations that determined the employees exposure were intended to identify employees who needed to be included in the hearing conservation program Therefore the measurements would have been made with the 80 dBA threshold and if a citation were to be issued the daily dose would have to be greater than or equal to 66 of the PEL In contrast if the evaluation had been intended to demonstrate compliance with the PEL or the need for engineering controls the 90 dBA threshold would have been appropriate and if a citation were to be issued the daily dose would have had to be greater than or equal to 132 percent of the PEL 2 In the cleaning department five workers polish small castings using hand held pneumatic polishing tools Seven additional workers at other tasks along the same wall in the cleaning department are similarly exposed to noise from the polishing tools There are no engineering controls The daily noise dose is 89 dBA to 93 dBA on
38. into the TWA This table limits short term noise exposure to a level not greater than 115 dBA for up to 15 minutes e Table G 16A This table presented in Appendix A of 29 CFR1910 95 provides information e g reference durations useful for calculating TWA exposures when the workshift noise exposure is composed of two or more periods of noise at different levels Although this table lists noise levels exceeding 115 dBA these listings are only intended as aids in calculating TWA exposure levels the listings for higher noise exposure levels do not imply that these noise levels are acceptable Additional information Links to App I A of the Noise eTool on the general industry standard is also available Construction Industry Noise in construction is covered under 29 CFR 1926 52 Occupational Noise Exposure and 29 CFR1926 101 Hearing Protection Under 29 CFR1926 52 employers are required to use feasible engineering or workplace controls when workers are exposed to noise at or above permissible noise exposures which are listed in Table D 2 1926 52 d 1 The PEL of 90 dBA for an 8 hour TWA is measured using a 90 dBA threshold this is the only threshold used for the construction industry noise standards 29 CFR1926 101 requires employers to provide hearing protectors that have been individually fitted or determined to fit by a competent person if it is not feasible to reduce noise exposure below permissible levels using engineering
39. law in acoustics and is shown in Figure 4 Section III Chapter 5 Page 11 Figure 4 Sound Pressure Levels in a Free Field source distance in meters If a point source in a free field produces a sound pressure level of 90 dB at a distance of 1 meter the sound pressure level is 84 dB at 2 meters 78 dB at 4 meters and so forth This principle holds true regardless of the units used to measure distance Free field conditions are necessary for certain tests where outdoor measurements are often impractical Some tests need to be performed in special rooms called free field or anechoic echo free chambers which have sound absorbing walls floors and ceilings that reflect practically no sound In spaces defined by walls however sound fields are more complex When sound reflecting objects such as walls or machinery are introduced into the sound field the wave picture changes completely Sound reverberates reflecting back into the room rather than continuing to spread away from the source Most industrial operations and many construction tasks occur under these conditions Figure 5 diagrams sound radiating from a sound source and shows how reflected sound dashed lines complicates the situation Figure 5 Original and Reflected Sound Waves original Section III Chapter 5 Page 12 The net result is a change in the intensity of the sound The sound pressure does not decrease as rapidly as it would in a free fi
40. of 90 dB is the equivalent of 100 dose The dose doubles every time the TWA increases by the exchange rate Table A 1 shows the relationship between dose and the corresponding 8 hour TWA exposure Example OSHA uses an exchange rate of 5 dB Suppose the TWA is 100 dB for an 8 hour exposure The dose doubles for each 5 dB increase over the criterion level of 90 dB The resulting dose is therefore 400 With an 8 hour TWA of 80 dB the dose would halve for each 5 dB below the criterion level The resulting dose would be 25 When taking noise samples of duration shorter than the full workday dose is an easy number to work with because it is linear with respect to time Example If a 0 5 hour screening sample results in 9 dose and the workday is 7 5 hours long the estimated dose for the full workday would be 135 7 5 0 5 x 9 This is computed making the assumption that the sampled noise will continue at the same levels for the full 7 5 hour workday While short term dose measurements cannot be used to support a citation they can be effectively used as a screening tool to determine whether full shift sampling is warranted Example A worker is employed in a high noise area for half an hour each day and the remainder of the 8 hour workday is spent in a quiet office area If the worker is exposed to 93 dBA for half an hour the dosimeter will read 10 Because no additional dose will Section III Chapter 5 Page 112 be accumulated while
41. or unwanted sound is one of the most common occupational hazards in American workplaces The National Institute for Occupational Safety and Health NIOSH estimates that 30 million workers in the United States are exposed to hazardous noise Exposure to high levels of noise may cause hearing loss create physical and psychological stress reduce productivity interfere with communication and contribute to accidents and injuries by making it difficult to hear warning signals This chapter provides technical information and guidance to help Compliance Safety and Health Officers CSHOs evaluate noise hazards in the workplace The content is based on currently available research publications OSHA standards and consensus standards The chapter is divided into six main sections Following this introduction the second section provides background information about noise and noise regulations and an overview of noise controls The third section describes worksite noise evaluations including noise measurement equipment noise evaluation procedures and noise sampling The fourth section offers investigative guidelines including methods for planning the investigation and outlines a strategy for conducting noise evaluations The fifth section describes noise hazard abatement and control including engineering and administrative controls hearing protection noise conservation programs cost comparisons between noise hazard abatement options and case studies
42. or workplace controls The requirements for permissible noise exposures and controls under the Construction standard are the same as those under the general industry standard 1910 95 though other requirements differ Continuing effective hearing conservation programs are required in all cases where the sound levels exceed the values shown in Table D 2 1926 52 d 1 When a hearing conservation program is required employers must incorporate as many elements listed in the Standard Interpretation titled Effective Hearing Conservation Program Elements for Construction Industry 08 04 1992 into their program as feasible Agricultural Worksites See OAR 437 004 0639 Noise Exposure Maritime Worksites Determine first if Oregon OSHA has jurisdiction over marine worksites Marine terminals and longshoring operations fall under the requirements of the general industry noise standard therefore employers in such operations must meet the elements of the general industry Hearing Conservation Amendment 29 CFR 1910 95 c through o Section III Chapter 5 Page 30 J Noise Exposure Controls Overview Noise controls should minimize or eliminate sources of noise prevent the propagation amplification and reverberation of noise and protect workers from excessive noise exposure Ideally the use of engineering controls should reduce noise exposure to the point where the risk to hearing is significantly reduced or eliminated Engineeri
43. permissible ultrasound exposure levels These recommended limits set at the middle frequencies of the one third octave bands from 10 kHz to 100 kHz are designed to prevent possible hearing loss caused by the subharmonics of the set frequencies rather than the ultrasound itself These exposure levels represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effects on their ability to hear and understand normal speech Table C 1 ACGIH also offers recommendations for measuring or verifying ultrasound levels which requires a precision sound level meter equipped with a suitable microphone of adequate frequency response and a third octave filter CSHOs considering evaluating ultrasound levels should consult the CTC for assistance in selecting a suitable instrument ACGIH also notes that Subjective annoyance and discomfort may occur at levels between 75 and 105 dB for the frequencies from 10 kHz to 20 kHz especially if they are tonal in nature Hearing protection or engineering controls may be needed to prevent subjective effects Tonal sounds in frequencies below 10 kHz might also need to be reduced to 80 dB ACGHI 2012 Section III Chapter 5 Page 124 Table C 1 Select Examples of Threshold Limit Values for Ultrasound Measured in Air 1 3 Octave Band Frequency Ceiling Values 8 Hour TWA kHz dB dB gt a S T o ooo a O re 20 u Pa head in air gt ACGIH s
44. reduction in air velocity Additional noise controls for high velocity air are presented in the retrofit and relocation sections below Surface or Panel Radiated Noise Machine casings or panels can be a source of noise when sufficient vibratory energy is transferred into the metal structure and the panel is an efficient radiator of sound Typically machine casings or large metal surface areas have the potential to radiate sound when at least one dimension of the panel is longer than one quarter of the sound s wavelength Conducting a thorough noise control survey will help in identifying the source of vibration and in determining the existence of any surface radiated sound When a machine casing or panel is a primary noise source the most effective modification is to reduce its radiation efficiency The following noise control measures should be considered Section II Chapter 5 Page 33 e Divide vibrating surface areas into smaller sections e Add stiffeners to large unsupported metal panels such as rectangular ducts or large machine casing sections e Add small openings or perforations to large solid surfaces e Use expanded metal when practical in place of thin metal panels e Add vibration damping material Retrofit Products and Applications A variety of commercially available acoustical products and applications can be applied on or relatively close to noise sources to minimize noise The Noise and Vibration Control Product
45. scale which has an unweighted flat response across the entire frequency spectrum from 10 Hz to 20 000 Hz The C weighted scale is also an acceptable option for octave band analysis because in the range of most workplace noise level measurements unweighted sound level measurements are less than dB higher than the corresponding C scale measurements The A weighted scale however is not an appropriate setting for octave band analysis because by definition it influences the meter response differently at various frequencies in the range of normal human hearing For a more detailed analysis the spectrum is sometimes measured in one third octave bands Although one third octave bands can be useful for noise engineers concerned with precise frequency measurements the standard single octave bands are sufficient for most evaluations performed by Oregon OSHA Whether detachable or integrated into a sound level meter an octave band analyzer receives its daily calibration in conjunction with the sound level meter with which it will be used This might involve activating an additional setting during the daily meter calibration Consult the user s manual for the equipment you will be using Question I ve heard that some sound level meters should be pointed at the noise source while others should be held at an angle e g 70 degrees 90 degrees Answer In many cases orientation makes no significant difference but it is always best to follow any re
46. spherical surface so that at any given point there exists a certain sound power per unit area This is designated as intensity Z and is expressed in units of watts per square meter Sound intensity is heard as loudness which can be perceived differently depending on the individual and his or her distance from the source and the characteristics of the surrounding space As the distance from the sound source increases the sound intensity decreases The sound power coming from the source remains constant but the spherical surface over which the power is spread increases so the power is less intense In other words the sound power level of a source is independent of the environment However the sound pressure level at some distance r from the source depends on that distance and the sound absorbing characteristics of the environment OTM Driscoll 8 Filtering Most noise is not a pure tone but rather consists of many frequencies simultaneously emitted from the source To properly represent the total noise of a source it is usually necessary to break it down into its frequency components One reason for this is that people react differently to low frequency and high frequency sounds Additionally for the same sound pressure level high frequency noise is much more disturbing and more capable of producing hearing loss than low Section III Chapter 5 Page 13 frequency noise Engineering solutions to reduce or control noise are differe
47. that the root cause or source cannot be effectively modified the next option for controlling undesirable vibration is to install vibration isolation Isolators come in the form of metal springs elastomeric mounts and resilient pads These devices serve to decouple the relatively solid connection between the source and the recipient of the vibration As a result instead of the vibratory forces being transmitted to other machine components or the building they are readily absorbed and dissipated by the isolators When selecting the appropriate isolation device s the person making the decision should consider the expertise of trained professionals It is critical to note that improper selection and installation of isolators can actually make a noise and vibration problem worse Many manufacturers of vibration isolation equipment have useful websites for troubleshooting problems and finding solutions see the Noise and Vibration Control Product Manufacturer Guide for a partial list of manufacturers Section III Chapter 5 Page 35 Some common applications for vibration isolation are e Pipe hangers e Heating ventilation and air conditioning HVAC equipment e Flex connectors for piping systems e Rotating machinery mounts and bases for electric motors compressors turbines fans pumps and other similar equipment e Impact equipment such as punch presses forging hammers or hammer mills and shearing presses e Enclosure isolation
48. the commonly used octave bands are listed in Table II 1 Table II 1 Octave Band Filters and Frequency Range rer Band Center Frequency TR Lower Band Limit Hz Cona Mirani Upper Band Limit Hz 22 44 31 5 250 500 1 000 2 000 4 000 8 000 16 000 Each octave band is named for its center frequency j N un RK eo Wn The width of a full octave band its bandwidth is equal to the upper band limit minus the lower band limit For more detailed frequency analysis the octaves can be divided into one third octave bands however this level of detail is not typically required for evaluation and control of workplace noise Section II Chapter 5 Page 14 Electronic instruments called octave band analyzers filter sound to measure the sound pressure as dB contributed by each octave band These analyzers either attach to a type sound level meter or are integral to the meter Both the analyzers and sound level meters are discussed further in Section HI 10 Loudness and Weighting Networks Loudness is the subjective human response to sound It depends primarily on sound pressure but is also influenced by frequency Three different internationally standardized characteristics are used for sound measurement weighting networks A C and Z or zero weighting The A and C weighting networks are the sound level meter s means of responding to some frequencies more than others The very low frequencies are discriminate
49. these are often the less experienced employees and supervisors and it is not unusual to find more problems in the after management normal working hours shifts 10 Does anyone check to see if you are wearing your hearing protection What happens if you are not 11 Do you routinely get new hearing protection when it wears out 12 Were you fitted for your hearing protection 13 Were you trained on how to wear your hearing protection properly Have worker demonstrate wearing hearing protection 14 Were you trained on how to use and care for your hearing protection Note the content of training and date of training 15 Have you ever been given a hearing test while working here 16 About how often do you get hearing tests 17 If so when was your last audiogram given 18 Who administers your audiogram 19 Do you have problems hearing e g tinnitus TTS 20 What is the frequency and duration of noise exposure Section III Chapter 5 Page 144 21 When would be the best day to return to sample for noise Note You want the worst typical noise exposure day to sample when the most machines are running 22 If the CSHO returns to conduct full shift sampling ask workers these additional questions 1 How often do you work on this machine e g hrs day days week days month 2 How many pieces are produced generated per day 3 Do the noise levels vary with customer specifications for specific materials
50. type of frequency analysis performed for workplace exposure evaluation and control An alternative frequency band the one third octave band is defined as a frequency band such that the upper band edge frequency f2 is the cube root of two times the lower band frequency f1 f2 or fi The level of detail provided by one third octave bands however is rarely required for occupational noise evaluation and control Peak noise The highest instantaneous sound level that a microphone detects Unlike the max level the peak is detected independently of the slow or fast response for which the unit is set Example The peak circuitry is very sensitive Test this by simply blowing across the microphone You will notice that the peak reading may be 120 dB or greater When you take a long term noise sample such as a typical 8 hour workday sample for OSHA compliance the peak level is often very high Because brushing the microphone over a shirt collar or accidentally bumping it can cause such a high reading the user must be careful not to place too much emphasis on the reading Permissible exposure limit PEL The A weighted sound level at which exposure for a criterion time typically 8 hours accumulates a 100 noise dose Only sounds 90 dBA and higher are integrated into the PEL i e the threshold level is 90 dBA Receiver A person exposed to noise that originates at a noise source If the receiver is exposed to a hazardous noise level the expo
51. user to estimate what portion of a worker s noise exposure comes from the direct sound field and what percentage results from reverberant sound When reverberant noise is a major contributor to a worker s daily noise exposure then adding sound absorbing materials may be beneficial Section III Chapter 5 Page 40 Sound Transmission Loss TL Materials Sound TL materials are used to block or attenuate noise propagating through a structure such as the walls of an enclosure or room These materials are typically heavy and dense with poor sound transmission properties Common applications include barriers enclosure panels windows doors and building materials for room construction All products sold for noise control should have a TL rating that is determined by ASTM standard It is important to note that TL rating varies with frequency TL values generally range from 20 to 60 dB with the higher number indicating superior attenuation properties For TL values of common building materials consult Table 9 12 in The Noise Manual AIHA 2003 or latest edition Acoustical Enclosures The acoustical enclosure is probably the most common path of treatment Quite often enclosures are used to address multiple noise sources all at once or when there are no feasible control measures for the source However there are a number of advantages and disadvantages associated with solid enclosures no acoustical leaks that must be considered by the user
52. violated iii NIOSH HHEs by Industry To access NIOSH HHEs that mention noise exposure levels or dosimetry data go to Health Hazard Evaluations and select Find an HHE Report In the search screen that appears search by keyword noise choose an industry category and limit the dates if desired Between 2000 and the end of 2011 NIOSH reported on 62 HHEs that included an evaluation of occupational noise exposure 2 Equipment Needed for Worksite Noise Evaluations You will need a sound level meter Type 2 or Type 1 and depending on the extent of the evaluation an octave band analyzer that is compatible with your sound level meter and noise dosimeters A noise instrument calibrator also will be required Additional equipment includes spare batteries for all instruments Check that you have the correct batteries Calibrators often require a different size battery than sound level meters or noise dosimeters Pack so that you have the following readily accessible tape measure preferably a 100 foot length pens and paper for sketching the worksite layout and standard noise measurement forms While conducting noise evaluations you should wear protective equipment appropriate for the site including hearing protection Keep earplugs or muffs with you at all times and wear them whenever you are in an area that the employer has designated as a noise hazardous zone e g by posting signs or if your escort tells you hearing protection is r
53. working in the quiet office area the equivalent 8 hour TWA will be 73 4 dBA as shown in Table A 1 Table A 1 Conversion Between Percent Noise Dose and 8 Hour TWA Sound Level a o oS oo J SS ooo o o SS Additional data points are provided in Table A 1 in Appendix A Section II of the noise standard 29 CFR 1910 95 particularly in the 80 999 dose range Exceedance level The level exceeded by the measured noise level for an identified fraction of time Exceedance levels may be calculated for many time fractions over the course of a shift and are typically expressed with percentages L For example an L40 equal to 73 dB would mean that for 40 of the run time the decibel level was higher than 73 dB Exchange rate or doubling rate The increase or decrease in decibels corresponding to twice or half the noise dose For example if the exchange rate is 5 dB 90 dB produces twice the noise dose that 85 dB produces assuming that duration is constant The OSHA exchange rate is 5 dB see Table D 2 of the construction noise standard 29 CFR 1926 52 and Tables G 16 and G 16a of the general industry noise standard 29 CFR 1910 95 Only instruments using a 5 dB exchange rate may be used for OSHA compliance measurements CSHOs should be aware that the following organizations use noise dosimeters with a 3 dB exchange rate NIOSH EPA ACGIH and most foreign governments The U S Department of Defense DOD previously used a 4 dB exch
54. years however many of the principles of noise control are as relevant now as they were decades ago Additionally considerable information is available in In this chapter Appendix K Three Ways to Jump Start a Noise Control Program Section VI Resources Subsections A and E On the Internet Washington State Department of Labor and Industries Noise Reduction Ideas Bank NIOSH s Industrial Noise Control Manual document number 79 1 17a World Health Organization s Engineering Noise Control 1 Source Treatment i Mechanical Impacts The driving force in a piece of equipment with a rotating part typically produces noise when the rotating part is out of balance or when the bearings are worn The sound typically increases as the speed of the rotation increases One simple cost effective way to reduce this noise is through preventive maintenance which includes properly lubricating and aligning moving parts For more information on controlling noise through preventive maintenance see Appendix K Three Ways to Jump Start a Noise Control Program Another way to reduce the noise generated by the driving force of a piece of equipment is to decrease the speed of the equipment The tradeoff with this approach is that in some processes there may be an associated loss in productive capacity In processes that involve impacts increasing the duration of impact while reducing the force can reduce the driving force as well This concept i
55. 11 Lecture Section III Chapter 5 Page 102 Driscoll Dennis P No date The Principles of Noise Control Associates in Acoustics Inc Lecture Driscoll Dennis P No date Room Acoustics V2 Associates in Acoustics Inc Lecture Government of Western Australia 2009 Department of Commerce WorkSafe Division Noise control fact sheet buying quiet Federal Register 1996 Health Standards for Occupational Noise Exposure in Coal Metal and Nonmetal Mines Proposed Rule 61 FR 66348 Dec 17 1996 HSE Health and Safety Executive 1995 Anti vibration treatment of high speed presses HSE Health and Safety Executive 1998 Control of noise at power presses Engineering Sheet No 29 HSE Health and Safety Executive 2005a Guidance bench grinder and linisher HSE Health and Safety Executive 2005b Powder Mill Koning M J LaLonde S Larner D Prime and A Tufnell 2003 Study of noise transmission from an electric router Lord H W W S Gatley and H A Evensen 1980 Noise Control for Engineers Krieger Publications Machinery Trader 2010 Product search for Komatsu D85EX 15 Last accessed August 2010 Mascus 2010 Product search for Komatsu D85A 21 Last accessed August 2010 Memtech No date Vibratory feeder bowl a case study in industrial sound dampening National Aeronautics and Space Administration No date Buy Quiet Process Roadmap NIOSH 2002 Pneumatic nail gun National Institut
56. 2502 S002 1000 zooo aoon Table V 4 Relative Transmission Loss for Example Materials dB TT E Cinder block Pain hollow 33 a aa fs Concrete Rear 6 in Panels perforated metal with mineral fiber insulator 4 in thick 28 34 40 48 56 62 Sheet metal laminate 2 1b ft viscoelastic core 15 25 28 32 39 42 Source Lord et al 1980 Sound absorbing materials are a valuable addition to acoustic enclosures and barriers which can interrupt a noise path Acoustic enclosures can be either full or partial and can surround either the noise source or the worker A personnel enclosure works best if it is lined with sound absorbing material An alternative is an enclosure that surrounds a piece of equipment a noise source as pictured in Figure 37 Employers and workers should consider the risk of equipment overheating when surrounded by an acoustic enclosure Partitions or barriers can be constructed when a total enclosure is not possible Barriers block mid and high frequencies better than low frequencies due to the greater diffraction of low frequency sounds Low frequencies can travel around corners and through holes whereas high frequency sounds are more likely to be blocked OTM Driscoll Section II Chapter 5 Page 83 Figure 37 Noise Barriers and Enclosures OTM Driscoll Sound absorption and reflection properties of different materials means that certain materials are better at interrupt
57. 3 dose according to the general industry standard CFR 29 1910 95 Convert this dose into an 8 hour TWA TWA 16 61 183 logio 90 94 4 dBA 100 Section III Chapter 5 Page 123 APPENDIX C Ultrasound Ultrasound is any sound whose frequency is too high for the human ear to hear The upper frequency that the human ear can detect is approximately 15 to 20 kilohertz or kHz although some people can detect higher frequencies and the highest frequency a person can detect normally declines with age Most of the audible noise associated with ultrasonic sources such as ultrasonic welders or ultrasonic cleaners consists of subharmonics Even though the ultrasound itself is inaudible the subharmonics it generates can affect hearing and produce other health effects C 1 Health Effects and Threshold Limit Values TLVs Research indicates that ultrasonic noise has little effect on general health unless there is direct body contact with a radiating ultrasonic source Reported cases of headache and nausea associated with airborne ultrasonic exposures appear to have been caused by high levels of audible noise from source subharmonics Subharmonics are sound waves with frequencies that are a fraction e g one half one quarter of the original ultrasound frequency Because they are lower than the ultrasound the human ear can detect them The American Conference of Governmental Industrial Hygienists ACGIH has established
58. A The equipment was removed from the cabinet and placed on pedestals which were mounted to the floor with rubber mounts As a result the noise level dropped to 91 dBA This control cost approximately 150 HSE 2005a v Insulation Enclosure Barrier Case study A company manufactured folding cartons The cartons were produced in stacks which were held together by uncut portions of the carton material The cartons were separated using an air chisel powered by compressed air This chisel generated noise levels of up to 95 dBA A simple barrier wall of 14 inch plywood was constructed consisting of a frame with plywood attached to either side The sound level of the receiver was reduced to 85 dBA vi Maintenance Case study A 20 ton press was used in a manufacturing process to pierce aluminum plates By replacing the bearings and providing proper lubrication when needed the noise levels were reduced between 7 dBA and 16 dBA These maintenance measures also increased the tonnage of the equipment to its original rating Case study NIOSH evaluated the noise exposure of heavy equipment operators using new and older models of bulldozers The newest bulldozer studied had noise controls consisting of acoustic foam on the ceiling of the rollover and falling object protection system an exhaust muffler and an enclosed engine compartment all missing on the older bulldozers Even with no cab the newest bulldozer had the lowest recorded operator s n
59. Appendix Bergstr m B and B Nystr m 1986 Development of Hearing Loss During Long Term Exposure to Occupational Noise A 20 Year Follow up Study Scand Audiol 15 227 34 Brandt Lassen R S P Lund and G B Jepsen 2000 Rats Exposed to Toluene and Noise May Develop Loss of Auditory Sensitivity Due to Synergistic Interaction Noise Health 3 9 33 44 Campo P and K Maguin 2006 Solvent Induced Hearing Loss Mechanisms and Prevention Strategy International Workshop on Health Effects of Exposure to Noise and Chemicals Ototoxicity of Organic Solvents Nofer Inst of Occup Med Lodz Poland November 15 16 conference report Campo P R Lataye and P Bonnet 1993 No Interaction Between Noise and Toluene on Cochlea in the Guinea Pig Acta Acoust 1 35 42 Campo P K Maguin and R Lataye 2007 Effects of Aromatic Solvents on Acoustic Reflexes Mediated by Central Auditory Pathways Toxicol Sci 99 2 582 90 Cappaert N L S F Klis H Muijser B M Kulig and G F Smoorenburg 2001 Simultaneous Exposure to Ethylbenzene and Noise Synergistic Effects on Outer Hair Cells Hear Res 162 1 2 67 79 Cappaert N L S F Klis H Muijser B M Kulig L C Ravensberg and G F Smoorenburg 2003 Differential Susceptibility of Rats and Guinea Pigs to the Ototoxic Effects of Ethyl Benzene Neurotoxicol Teratol 24 503 10 Cary R S Clarke and J Delic 1997 Effects of Combined Exposure to Noise and Toxic Subs
60. III Chapter 5 Page 137 General guidelines provided by AIHA General guideline 1 Whenever possible include noise control at the design phase equipment or facilities Considering noise exposure only at a later stage and then retrofitting existing equipment can cost more than 10 times as much as designing the noise control before construction begins The cost of purchasing new production equipment comes into play somewhere between the two General guideline 2 Include maintenance expenses in the cost estimate unless more specific information is available assume that these can run about 5 per year e g for 10 years Source Driscoll and Royster 2003 Number of participants in the hearing conservation program e Hearing protection devices e Noise surveys e Audiometric testing e Audiometric follow up and retests e Recordability determination e Worker training materials e Calibration of acoustical instrumentation e Calibration of audiometers e Worker training time e Worker hearing test time e Hearing conservation program administrative time e Maintenance of acoustical instrumentation e Lost production e Space allocation e Expense to certify CAOHC Council for Accreditation in Occupational Hearing Conservation technicians e Medical record retention e Workers compensation Using this method the cost of the hearing conservation program does not include machinery present or future In 2010 and 2011 a
61. LS an average labor rate of 27 hour 2010 rate could be assumed when considering installation costs regional rates could be more or less Sources BLS 2009a b mye mje Q nln 5 5 S O ion ojoo m a o SIEBIE S Q ols a al 5 Ra E aml mi 2 sles S Sy ele 2 eg e n S 3 3 a S O slo fale Oo o a ch 2 2 Bs 2 Sl z A oa e lt O On N oOo lt 4 Q O oO n n 2 2 m O 6 n oO F G g io Nn J Q S D va ag i da When additional information is on hand the CSHO may also make an informed decision about using the low or high end of the cost range instead of the average Select the high end of the cost range for larger sizes of equipment materials with extra thickness situations that require Section III Chapter 5 Page 101 high precision or specialty parts locations with higher costs of living or when other factors tip the selection toward the more costly option VI References Acoustical Solutions 2012 Glossary of Terms Acoustical Solutions Inc Accessed April 2012 ACGIH 2003 TLVs and BEIs Threshold Limit Values for Chemical Substances and Physical Agents amp Biological Exposure Indices p 107 Allied Witan 2010 Personal communication between John Gibble of Allied Witan and Eastern Research Group Inc June 7 AIHA 2003 The Noise Manual 5th edition Edited by E H Berger et al Fairfax
62. Measuremem conducted fool adove case Hade SOUND LEVEL dBA Before 94 2 dBA After 85 2 dBA TOE E T as o p i o oal ae oa o ai 1 3 OCTAVE BAND FREQUENCY Hz m Before Adjustment 94 2 dBA Aler Adjustment 85 2 dBA Acoustical Maintenance Maintaining all equipment and noise controls at their optimum performance condition needs to be an on going effort Hand in hand with general mechanical maintenance which improves the performance and life span of any piece of equipment an acoustical maintenance program will help ensure the equipment remains within the noise limits intended by the company or as the equipment should generate under optimal working conditions Section III Chapter 5 Page 173 Acoustical Maintenance As criteria for an acoustical maintenance program each machine should typically operate within 2 dBA of the minimum sound level of which it is optimally capable Plus when equipment is maintained in good working order from a noise exposure standpoint the added benefit is that it will minimize the time workers need to spend in the direct sound field of the machine while performing any service requirements Acoustical Maintenance To assist with implementing an effective acoustical maintenance program the following elements are presented Conduct an initial baseline sound level survey for each machine in good working order while operating under normal conditions This should
63. NSI ASSE A10 46 2007 under the Hearing Loss Prevention heading Noise N avigator Sound Level Database 2008 An extensive database of over 1 700 sound level measurements reported by various references for a wide range of equipment and activities occupational recreational and military noise sources A reference for each source is provided The Intro tab of this Excel spreadsheet introduces the spreadsheets in which the sound level measurements are organized This database is compiled by E A R Aero Company and the University of Washington as of spring 2012 the current version 1 4 is dated 2008 Noise Database for Prediction of Noise on Construction and Open Sites 2005 Eight tables reporting average measurements for noise from equipment used on construction and open sites in the United Kingdom UK Organized by construction phase and type noise level information includes both unweighted octave band Leg levels and overall A weighted Leq values in decibels This document was commissioned by the UK government and published in 2005 Noise Emissions for Outdoor Equipment This European Commission database lists operating noise levels for several dozen categories of outdoor equipment The European Commission requires equipment manufacturers to accompany their equipment with a declaration of conformity stating that the equipment conforms to the provisions of noise limiting directives issued by the European Community governing organi
64. Reduce Pneumatic and Compressed Air Systems A special case of high velocity fluid flow is compressed air which is used widely for many purposes such as e Blowing debris off parts and surfaces e Moving products on assembly lines e Spraying paint and other substances e Driving pneumatic tools Compressed air causes noise exposure in most major industry sectors Because compressed air is so common and loud it accounts for a large percentage of all workplace noise exposure Fortunately noise from compressed air sources is easy and relatively inexpensive to abate Examples of options for reducing noise from compressed air include e Adjusting the pressure regulator to reduce the air pressure in the air line coming from the compressor to the minimum pressure needed to accomplish the task Lower pressure is not only quieter but it saves energy and is safer To reduce serious injuries OSHA requires that air pressure be held to 30 pounds per square inch or less when it could potentially contact skin e Replacing noisy air nozzles guns and wands with quieter models that have built in noise control features Some models produce strong air thrust while reducing noise using less compressed air and saving energy Figure 30 e Installing additional air pressure control valves so air lines can be controlled individually to their effective minimum e Retrofitting pneumatic tools compressors and machinery by adding pneumatic mufflers or inli
65. SHOs The Oregon OSHA Laboratory also coordinates periodic factory calibration of any Oregon OSHA owned noise monitoring instruments that it does not service directly Employers that lease or own Type I or Type II noise measuring instruments can arrange annual calibration of the equipment through the equipment supplier or manufacturer During periodic calibration the Oregon OSHA Laboratory also performs preventive maintenance to ensure that the equipment remains fully functional over its life expectancy If the Oregon OSHA Laboratory detects a problem it services the instrument as necessary When returning equipment to the Oregon OSHA Laboratory for periodic calibration be sure to include a note about any problems or concerns with equipment function so they can be evaluated as part of the maintenance process If equipment is not functioning well the Oregon OSHA Laboratory requests that the instrument be returned for inspection even if it is not yet due for calibration Octave band analyzers that are integrated into a sound level meter will be calibrated as part of the sound level meter However detachable octave band analyzers must be returned to the Oregon OSHA Laboratory for periodic calibration with the meter with which they are intended to be used Pre and post calibration procedures confirm that the instrument is functioning properly on the day that it is used and prove that it is still registering sound levels correctly at the end of t
66. STD 1 4 1A Enforcement of the Occupational Noise Exposure Standards 29 CFR 1910 95 1926 52 and 1926 101 Inspection Procedures and Interpretive Guidance can be used to provide assistance with the cost comparison process During the closing conference it is important to explain how each of the proposed citations presents a hazard and why you are proposing it It is in everyone s best interest to understand the significance of the hazard and not just that it is a violation Employers react more favorably when there are no surprises in the citations It is also important to listen at the closing there may be information that can affect the citation 2 After the cost comparison is complete and it has been determined that the cost of engineering controls is less than the cost of a hearing conservation program write a Section III Chapter 5 Page 150 citation for 29 CFR 1910 95 b 1 In addition cite for any deficiencies in the employer s hearing conservation program 3 Another scenario may involve an 8 hour TWA exposure gt 100 dBA 90 dBA threshold and hearing protection alone may not reliably reduce noise levels to levels specified in Tables G 16 or G 16a of the standard economic feasibility or cost comparison is not necessary in this situation The CSHO researches examples of technically feasible engineering controls for the specific machine and or process contributing to the noise levels Start with easy solutions first O
67. Section II 2 OSHA Noise Standards for more information The standard for short term noise levels is distinct from Oregon OSHA s instantaneous ceiling limit of 140 dBA for impact noises occurring less frequently than one per second and typically measured using a sound level meter set to the fast response setting You will need to make other decisions regarding dosimeter setup For example the typical noise dosimeter offers several options for the frequency with which noise is sampled and data logged The more frequently the data are logged the more data points are stored and the larger the file eventually will be The calibrated noise dosimeter fastens to the worker s belt while the microphone clips to the shoulder or lapel Orient the microphone so it points straight up you might need to adjust the clip to find a functional position Avoid positioning the microphone where it could become enfolded in clothing or rub against cloth or other materials both of which could influence the results If appropriate run the microphone cable under the worker s outer layer of clothing to keep it out of the way and prevent it from snagging on objects in the work area The dosimeter can hang inside the outer layer of clothes as well an advantage in wet weather but the microphone must remain in the open air without contacting other surfaces except the base on which it clips Section III Chapter 5 Page 58 Some dosimeter models are capable of
68. Section III previously Section II of Oregon OSHA s Technical Manual a HEALTH HAZARDS CHAPTER 1 POLYMER MATRIX MATERIALS j ADVANCED COMPOSITES QO CHAPTER 2 INDOOR AIR QUALITY 2 INVESTIGATIONS m a QO CHAPTER 3 VENTILATION INVESTIGATIONS LLJ CHAPTER 4 HEAT STRESS CHAPTER 5 NOISE CHAPTER 6 LASER HAZARDS CHAPTER 7 LEGIONNAIR S DISEASE All information within this section and chapter has been reproduced from the Oregon OSHA Technical Manual circa 1996 unless otherwise stated within the Chapter Revision Information located at the beginning of each chapter Section III Chapter 5 Page 1 SECTION III CHAPTER 5 NOISE Chapter Revision Information e This chapter was previously identified as NOISE MEASURMENTS in Section II Chapter 5 of Oregon OSHA s circa 1996 Technical Manual The section number was modified to Section II in March 2014 to provide uniformity with federal OSHA s Technical Manual OTM In March 2014 the original NOISE MEASURMENTS chapter was replaced by federal OSHA s October 25 2013 updated chapter NOISE In March 2014 several references to federal OSHA CPLs Directives Field Operations Manual and FOM were revised when appropriate to reflect Oregon OSHA s Field Inspection Reference Manual FIRM as well as Oregon OSHA s Program Directives _ lt lt 2 l lt Z JE Q En _ In March 2014 Section IIT Measurements
69. Section III Chapter 5 Page 94 is less than or equal to the cost of a continuing effective hearing conservation program for all the workers who would benefit from the control s implementation 1 e have a reduction in their noise exposure Assumption 7 If actual costs of administrative controls are known to the CSHO then they should be used Where administrative controls are feasible but the costs are unknown no additional costs will be assumed for cost estimation purposes Assumption 8 If the actual cost of a production penalty for a control option is known to the CSHO then it should be used If unknown no production penalty will be assumed for cost estimation purposes Assumption 9 If a proposed noise control would also address another hazard e g machine guarding ventilation hood then the cost of the noise control shall be deemed feasible because these other controls do not require an economic feasibility analysis Assumption 10 If actual hearing conservation program costs are known to the CSHO then they should be used If unknown use an assumed figure of 375 worker year the average of the range provided in Appendix G 1 2 of this chapter If applicable use Table V 5 to adjust this unit cost based on the number of workers in the hearing conservation program at this worksite Assumption l1 Maintenance problems e g bad bearings steam leaks that result in excessive workplace noise levels are cited under the engineerin
70. _ e w o o o ee ee ee 1 3 OCTAVE BAND FREQUENCY Hz Section II Chapter 5 Page 179 Machine Guarding and Acoustical Benefits Poly Carbonate Safety Enclosures Seal off all small gaps and openings along all polycarbonate panel edges and the adjacent framework and the bottom edge of the machine cabinet to the floor Keep in mind the graph showing loss of attenuation due to small percent openings All door panel seals need to be airtight to maximize the noise reduction benefit Ruk of Thumb A 1 opening can reduce Ha attenuation by at least 10 dBA Section III Chapter 5 Page 180 Machine Guarding and Acoustical Benefits 1 For all existing polycarbonate guards tightly seal or at least minimize all gaps or openings between the panel edges and their frame and between all adjacent metal frame sections 2 For sealing polycarbonate enclosures with large openings such as gaps between the floor and bottom edge of the machine cabinet use a dense but flexible barrier material Machine Guarding and Acoustical Benefits 3 Install at least some sound absorption material to at least 25 of any available surface areas inside the enclosures The material s location in not critical as it just needs to be inside the enclosure Section III Chapter 5 Page 181 Three Significant Home Runs 1 Get a handle on pneumatic and compressed air devices and machine controls 2 Implement an Aco
71. a Welding Manual material handling osa Other tasks Layout o ooo CEMENT MASONS Floor leveling Placing concrete Break rest lunch cleanup Repairing concrete Setting forms Manual material handling ELECTRICIANS Operating work vehicle om2 Installing slab conduit Sheet metal work slo Installing wall conduit Manual material handling 86 5 Installing cable tray m i g E Finishing concrete osa Patching concrete E Panel wiring installing fixtures Pulling wire Break rest lunch cleanup Installing trench conduit Section II Chapter 5 Page 27 Sheet metal work 778 Other tasks Applying insulation by hand osgo Manual material handling Break rest lunch cleanup o 83 fj 7 sd Operating forklift 87 1 Manual materials handling Setting forms 87 9 Other tasks Operating work vehicle Tying and placing rebar Erecting iron Break rest lunch cleanup Grinding Rigging Bolt up Layout Placing concrete Manual material handling Stripping forms Interior finish Building forms Operating forklift Break rest lunch cleanup Rigging Grouting Other tasks Finishing concrete Wood framing Demolition Floor leveling Bricking blocking tiling Break rest lunch cleanup Forklift operation Grinding P Grouting tending mortaring Rigging Grade checking Other tasks Welding Source Adapted from Seixas and Neitzel 2004 Chipping concrete I Regulat
72. about extended workshift sampling see Appendix H 3 Hearing Conservation Program If the walkaround has not yet been completed follow through by investigating noisy locations in person If the walkaround has already been conducted review your noise measurements taken at high noise level operations Where workers are exposed to noise at the AL or higher examine the employer s hearing conservation program Check that the program includes the basic elements of a hearing conservation program e g monitoring training noise exposure reduction measures audiometric evaluation and that noise exposed workers are enrolled in the program Look for Section II Chapter 5 Page 67 evidence that noise exposed workers are receiving hearing conservation training and have been fitted with and taught to use their HPDs correctly Confirm that the employer provided a choice of hearing protectors and that this personal protective equipment provided an appropriate level of protection for the workplace noise level For more information about determining whether the attenuation of a HPD is sufficient see Appendix E C Conducting the Walkaround Evaluation The walkaround inspection is a chance for you to see the workers working conditions first hand and to measure noise levels using the sound level meter or noise dosimeter set to operate as a sound level meter Use your senses to identify areas that might have hazardous noise and then use the sound level
73. act The dosimeter calibration process is nearly identical to that for sound level meters Frequently for a given brand of instruments the same calibrator can be used for a manufacturer s sound level meters and noise dosimeters Figure 22 Noise dosimeters routinely must run for 8 to 10 hours per day This means battery function is particularly important Some models might require new batteries each day of use Just as for sound level meters each dosimeter must receive periodic calibration every 12 months and a daily calibration and battery check before each use They also require a post use calibration check The documentation procedures are the same as those for sound level meters Figure 22 Calibrator Adapter Always consider the accuracy of noise measuring equipment when using readings for compliance purposes Like Type 2 sound level meters Type 2 noise dosimeters have an implied accuracy of 2 dBA To prove an overexposure the 8 hour TWA sound level L TWA must be 2 dBA over the PEL In practice the workers are overexposed to noise with an 8 hour TWA of 92 dBA a dose of 132 as measured at the 90 dBA threshold setting of the dosimeter and an average sound level of 92 dBA Workers must be included in a hearing conservation program when measured noise levels are 87 dBA as an 8 hour TWA a dose of 66 of the PEL as measured at the 80 dBA threshold setting Section III Chapter 5 Page 57 ii Using Noise Dosimeter
74. alculates the wavelength of any airborne noise frequency in inches feet and meters C Hearing Loss 1 Hearing Loss Reporting Council for Accreditation in Occupational Hearing Conservation 2005 Determining When Hearing Loss Is Work Related 2 Hearing Loss Incident Rates Bureau of Labor Statistics 2011 TABLE SNRO8 Incidence Rates of Nonfatal Occupational Illness by Industry and Category of Illness 2010 This extensive table lists by industry the incidence of reported illnesses per 10 000 full time workers The table includes a column for hearing loss BLS publishes this information annually each fall covering the previous year s data Check for the latest edition and previous years here 3 Hearing Loss Prevention American National Standards Institute American Society of Safety Engineers 2007 Hearing Loss Prevention for Construction and Demolition Workers ANSI ASSE A10 46 2007 This ANSI document recommends standards for hearing conservation programs for construction and demolition workers Recommendations cover hazard identification hazard control hearing protection devices audiometry training recordkeeping and program evaluations An appendix lists noise levels in Section III Chapter 5 Page 107 decibels that are likely to be exceeded by several dozen different construction activities and cites a source for each listed level D Sound Levels of Equipment Occupations and Activities See also A
75. als including solvents was recognized The possibility of noise solvent interaction was raised more recently when Bergstr m and Nystr m 1986 published the results of a 20 year epidemiological follow up study in Sweden started in 1958 and involving regular hearing tests in workers Interestingly a large proportion of workers employed in the chemicals divisions of companies suffered from hearing impairment although noise levels were significantly lower than those in sawmills and paper pulp production The authors suspected that industrial solvents were an additional causative factor in hearing loss Workers are commonly exposed to multiple agents Physiological interactions with some mixed exposures can lead to an increase in the severity of harmful effects This applies not only to the combination of interfering chemical substances but also in certain cases to the co action of chemical and physical factors In this case effects of ototoxic substances on ear function can be aggravated by noise which remains a well established cause of hearing impairment According to the European Agency for Safety and Health at Work 2009 experiments with rats have shown that combined exposure to noise and solvents induced synergistic adverse effects on hearing Good evidence has been accumulated on the adverse effects on hearing of the following solvents Toluene ethylbenzene n propylbenzene Styrene and methylstyrenes Trichloroethylene p Xylene
76. als and Application 2nd edition New York NY Marcel Dekker Inc Bruce R D A S Bommer and C T Moritz 2003 Noise Vibration and Ultrasound In The Occupational Environment Its Evaluation Control and Management 2nd edition Fairfax VA American Industrial Hygiene Association pp 435 475 Cheremisinoff N 1996 Noise Control in Industry A Practical Guide Westwood NJ Noyes Publications Cox T J and P D Antonio 2004 Appendix A In Acoustic Absorbers and Diffusers Theory Design and Application New York NY Spon Press Diehl George M 1973 Machinery Acoustics Wiley Interscience New York NY NIOSH 1980 Compendium of Materials for Noise Control DHEW NIOSH Publication No 80 116 NIOSH 1978 Industrial Noise Control Manual DHHS NIOSH Publication No 79 117 Section III Chapter 5 Page 106 This manual includes 61 case histories on noise control modifications for industrial processes and equipment It displays decibel and octave band analysis of noise levels before and after control methods were applied It also presents relative costs of many control methods in 1978 dollars Peterson A P G 1980 Noise and Vibration Control In Handbook of Noise Measurement 9th edition Concord MA GenRad Inc pp 239 259 World Health Organization No date Engineering Noise Control B Noise Physics M Squared System Design Group Inc No date Wavelength of sound calculator This tool c
77. anal Inner Ear Auricle Tympanum Pinna Eardrum m Eustachian Outer Ear Middle Ear Tube OTM Driscoll The function of the ear is to gather transmit and perceive sounds from the environment This involves three stages e Stage 1 Modification of the acoustic wave by the outer ear which receives the wave and directs it to the eardrum Sound reaches the eardrum as variations in air pressure e Stage 2 Conversion and amplification of the modified acoustic wave to a vibration of the eardrum These vibrations are amplified by the ossicles small bones located in the middle ear that transmit sound pressure to the inner ear The vibrations are then transmitted as wave energy through the liquid of the inner ear the cochlea e Stage 3 Transformation of the mechanical movement of the wave into nerve impulses that will travel to the brain which then perceives and interprets the impulse as sound The cilia of nerve cells in the inner ear called hair cells respond to the location of movement of the basilar membrane and depending on their position in the decreasing radius of the spiral shaped cochlea activate the auditory nerve to transmit information that the brain can interpret as pitch and loudness Impaired function at any of these stages will affect hearing Additional information on the outer ear middle ear and inner ear is available in OSHA s eTool links to Noise eTool App I B Section II Chapter 5 Page
78. and it improves communication It is also a time to get useful employer statements e g Yes this has been a long standing problem but corporate doesn t want to spend the money now That just broke we have a new muffler on order I can show you the PO achieve consensus on possible fixes and point out problems that the employer may really not have known about It is also a good time for practical instruction so that the employer walks away with an understanding of the problem its significance and possible solutions d Record the condition of the machine find out who performs maintenance on machine equipment and review any maintenance records e Record machine operation e g speed cycle part min f List noise sources for worker primary secondary tertiary g Identify existing controls h Measure distance from worker to the primary noise source i Ask whether the worker s presence in the noise field is required for the job j Ask questions about hearing protection type properly worn worn at all times choices of hearing protection offered is the attenuation sufficient for the worker s noise exposure k Observe how worker is wearing hearing protection e g foam plugs if worn incorrectly take a picture In addition to noting the type of hearing protectors the sampled worker is wearing it is also important to note whether i Other workers in the area are wearing hearing protection ii Workers passing t
79. ange rate however all branches except the U S Navy now have adopted the 3 dB exchange rate Hertz Hz Unit of vibration frequency numerically equal to cycles per second Section II Chapter 5 Page 113 Impact noise or impulsive noise Impact noise is created by the impact of one surface on another and is of a short duration Impulsive noise is typically an air noise that has a short duration such as the shooting of a firearm or the explosion of a firework The standard states that exposure to impulsive or impact noise should not exceed a 140 dB peak sound pressure level Impulsive or impact noises are considered to be much more harmful to hearing than continuous noises In construction most of the 500 000 workers who are exposed to hazardous noise levels are also exposed to impulsive and impact noise sources on worksites Impulsive and impact noise is typified by a sound that rapidly rises to a sharp peak and then quickly fades Both are transient noises of brief duration and high intensity The sound may or may not have a ringing quality such as a striking a hammer on a metal plate or a gunshot in a reverberant room Impulsive noise can be repetitive or a single event like a sonic boom if impulses occur in very rapid succession such as with some jack hammers it is not described as impulsive or impact noise Intensity of sound Intensity of sound is measured in watts per square meter To calculate the intensity level in decibel
80. application to help calculate the cost benefit ratio for potential noise reduction projects A white paper explains the approach used to determine the costs of exposing a person to noise for the length of a career Nelson 2012 This method uses the following factors to estimate the cost of noise exposure The TWA noise exposure presumed constant over time The net present value NPV of potential disability claims at the end of 30 years The NPV of hearing aids and batteries that might be needed after retirement The NPV of the hearing conservation program and personal protective equipment during the career The white paper offers the following note about use of the NPV The economic benefit of noise control is estimated by comparing the reduction of the net present value of noise exposure to the cost of the corresponding noise control effort For purposes of this paper the discount rate for the NPV calculation is assumed to be 0 inflation neutral The NPV is then just the sum of the expected expenditures in today s dollars This assumption translates in practice to the expectation that all inflated future costs will be paid with equally inflated future dollars out of available cash accounts The white paper cites a 2006 study commissioned by the U S Navy titled Long term Cost Benefit of Noise Control on Ships Bowes et al 2006 Extrapolating the cost per year and adjusting for inflation the NPV of the hearing conservatio
81. ard is called the Safe In Sound award General guidelines General guideline 1 Plan to complete two noise control projects per year General guideline 2 Noise reduction projects often have additional benefits such as reduced energy requirements cleaner facilities and improved machinery performance or service life Sources Driscoll 2010 2012 Colgate Palmolive 2012 Colgate Palmolive won the 2012 Safe In Sound award through an extensive effort to reduce noise exposure in its facilities around the world NIOSH 2012 With the assistance of a noise control engineer and following the general principles outlined by AIHA Colgate Palmolive identified and prioritized noise sources The process revealed that compressed air accounted for approximately 30 of the noise at production facilities and required approximately 15 of the energy To help solve both problems the company created Noise Energy amp Maintenance teams to help the company optimize system operation minimize leaks and assist workers in using compressed air appropriately They planned to execute two noise reduction projects per year at many sites As of 2012 the company had completed 250 noise reduction projects across 60 facilities investing 2 million The results averaged approximately 6 dBA noise reduction per project and up to 22 dBA for some projects Noise exposure was reduced for more than 5 000 workers through these projects the math suggests that this e
82. atment i Sound Absorption Reflected sound sound reverberating from the walls ceiling and floor will add to the sound wave propagating directly from the source to the receiver thus increasing the overall noise level within a room Acoustical absorptive materials are used to reduce this reflected sound installed on the walls or ceiling Figure 36 they absorb and dissipate the sound before it can be reflected Materials used for sound absorption are usually porous or fibrous e g fiberglass mineral wool felt polyurethane foams Figure 36 Sound Absorption Paneling Driscoll Principles of Noise Control Section III Chapter 5 Page 79 The room shown in the figure has been treated with absorption panels in the ceiling space Note that adding this material to reduce the reverberant sound does not reduce the direct sound coming from the equipment that sound will always exist even if the equipment is placed outside where little to no reflection exists When treating a ceiling with absorptive material a useful guideline is that the noise level will not be significantly reduced for workers at ground level when acoustical panels are installed at ceiling heights greater than 15 feet In this situation workers are most likely affected primarily by the direct sound wave Vertically hung panels can create new problems such as interference with ventilation lighting and sprinkler patterns Also for this form of treatment to provide
83. by mechanical impacts high velocity fluid flow high velocity air flow vibrating surface areas of a machine and vibrations of the product being manufactured Mechanical Impacts To reduce noise caused by mechanical impacts the modifications outlined below should be considered For any of these options to be practical however they must not adversely affect production e Reduce excessive driving forces e Reduce or optimize speed e Minimize distance between impacting parts e Dynamically balance rotating equipment e Maintain equipment in good working order e Use vibration isolation when applicable Section III Chapter 5 Page 32 High Velocity Fluid Flow High velocity fluid flow can often create excessive noise as the transported medium passes through control valves or simply passes through the piping Frequently noise is carried downstream by the fluid and or vibratory energy is transferred to the pipe wall A comprehensive acoustical survey can isolate the actual noise source so that the appropriate noise control measures can be identified When deemed practical some effective modifications for high velocity fluid flow noise include e Locate control valves in straight runs of pipe e Locate all L s and T s at least 10 pipe diameters downstream of a valve e Ensure that all pipe cross section reducers and expanders are at an included angle of 15 to 20 degrees e Eliminate sudden changes of direction and influx of one
84. c substances including toluene styrene ethylbenzene and trichloroethylene About IMIS Data In reviewing IMIS data note that the exposure levels are not necessarily typical of all worksites and occupations within an industry Rather IMIS provides insight regarding the noise exposure levels for workers in the jobs that OSHA monitored while visiting workplaces Typically OSHA identified those jobs as having some potential for noise exposure A number of epidemiological studies have investigated the noise solvent relationship in humans Overall the evidence strongly suggests that combined exposure to noise and organic solvents can have interactive effects either additive or synergistic in which solvents exacerbate noise induced impairments even though the noise intensity is below the permissible limit value In addition to the synergistic effects with solvents noise may also have additive potentiating or synergistic ototoxicity with asphyxiants such as carbon monoxide and metals such as lead See Appendix D for additional information and additional sources of information on this topic Section II Chapter 5 Page 22 H Affected Industries and Workers 1 Affected Industries Workplace noise exposure is widespread Analysis of OSHA s Integrated Management Information System IMIS data for 1979 through 2006 showed that workers were exposed to hazardous noise levels in every major industry sector Although this time span cover
85. cal solution Lagging essentially a localized form of enclosure can be wrapped around pipes or ducts that generate noise The lagging should be designed following the same principles outlined for enclosures with effective barrier materials on the outside and sound absorptive materials on the inside Lagging is generally installed from the inside out by first encircling the pipe or duct with the absorptive inner material then applying an airtight limp barrier material as a protective covering The airtight outside barrier of the lagging can be composed of asphalt paper linoleum neoprene sheeting lead loaded vinyl or other materials with similar qualities Placed against the pipe or duct the lagging s inner absorptive material provides isolation between the outer layer and the noise source and also helps absorb noise from the source Section III Chapter 5 Page 87 v Shields or Barriers A barrier is a partial wall or partition between the noise source and the receiver It is made of a solid dense material with high sound transmission loss Sound barriers create a sound shadow at the location of the receiver thus attenuating noise exposure Figure 41 Large Partition Wall Driscoll Principles Noise Control a Note the large partition wall on the right side of the photograph in Figure 41 A barrier should be as tall as possible and be as close to the worker or the noise source in between the two as feasible in order to max
86. cochlea Even moderate noise can cause twisting and swelling of hair cells and biochemical changes that reduce the hair cell sensitivity to mechanical motion resulting in auditory fatigue As the severity of the noise exposure increases hair cells and supporting cells disintegrate and the associated nerve fibers eventually disappear Occupational noise exposure is a significant cause of sensorineural hearing loss which appears on sequential audiograms as declining sensitivity to sound typically first at high frequencies above 2 000 Hz and then lower frequencies as damage continues Often the audiogram of a person with sensorineural hearing loss will show a Notch at 4 000 Hz This is a dip in the person s hearing level at 4 000 Hz and is an early indicator of sensorineural hearing loss Results are the same for hearing tests of the ear and bone conduction testing Sensorineural hearing loss can also result from other causes such as viruses e g mumps congenital defects and some medications Figure 8 shows the typical audiogram patterns for people with conductive and sensorineural hearing loss Section III Chapter 5 Page 18 Figure 8 Audiograms Sensorineural Hearing Loss Audiogram Conductive Hearing Loss Audiogram Frequency in Hertz Hz Frequency in Hertz Hz 250 500 1000 2000 meee Hearing Level HL in dB Re ANSI 1969 a z lt x a 3 amp Si D z Additional information lin
87. commendation from the manufacturer Such a recommendation would be based on microphone type Typical recommendations include Free field microphones point directly toward the noise source a O degree angle CSHOs should consult with the Oregon OSHA Laboratory regarding the microphone models provided with their sound level meters Section III Chapter 5 Page 53 Figure 19 Octave Band Analyzer Settings and Center Frequencies 61 5 500Hz 55 1 4kHz 57 9 2kHz 53 5 4kHz 426 8kHz 43 0 16kHz QQ 7 ps a c z F METER 1 b Tabulation screen Press Enter center arrow key to switch screens Sample bar chart screen A selected frequency band 250 Hz ini example B selected frequency in curve C amplitude dB in band Tabulation screen lists amplitude in dB for each frequency band ii Using the Octave Band Analyzer The Type 1 sound level meters used by Oregon OSHA such as the 3M SoundPro have built in octave band analysis capability Some other models of sound level meter are designed to work with a separate octave band analyzer that is physically attached to the meter Figure 20 In either case the sound level meter microphone operates normally but the noise signal detected by the microphone is separated into its component frequencies When the octave band analyzer is activated and a particular frequency band selected the meter readout provides the decibel level associated with that frequency
88. corded during your noise screening 6 If workers are on an extended workshift then you must calculate a revised AL using the formula in Section IV B 2 Extended Workshifts in this chapter Section III Chapter 5 Page 145 H 4 Full Shift Sampling 1 Pre calibrate noise dosimeters sound level meters and octave band analyzers fully document calibration on proper OSHA forms At the start of workshift or immediately after an abbreviated opening conference place noise dosimeters on workers If related to a complaint or referral be careful to first select workers who will address any specific concerns in the referral or complaint as these items must be addressed The other workers should be selected based on highest anticipated exposures a Explain to each worker being sampled who you are why you are there and the purpose of the dosimeter Emphasize that the dosimeter is not a speech recording device Explain as part of the documentation that you will be taking pictures of them doing their work and to show how the dosimeter was worn b When the dosimeter is positioned generally at the waist clip the microphone to the worker s shirt collar at the shoulder close to the worker s ear Clips should be placed in accordance with manufacturer s instructions Position and secure any excess microphone cable to avoid snagging or inconveniencing the worker If practical the cord should run under the worker s shirt or coat If possib
89. cturing Fabricated Metal Product 20 549 88 86 44 27 13 Manufacturing Machinery Manufacturing 10 156 86 22 e oe Oe Computer and Electronic 85 28 29 23 Product Manufacturing Electrical Equipment 3 889 86 54 32 22 Appliance and Component Manufacturing Transportation Equipment 7 812 88 36 41 24 12 Manufacturing Furniture and Related 5 292 87 83 38 27 Product Manufacturing Miscellaneous 2 770 86 78 35 24 Manufacturing Section III Chapter 5 Page 25 2 Historically Affected Jobs in General Industry Noise is a potential hazard for most jobs that involve abrasive or high power machinery impact of rapidly moving parts product or machinery or power tools According to IMIS noise measurements workers in certain occupations within specific industries are exposed to excessive noise more frequently than others While many jobs have noise exposure historically some of the occupations with the most extreme exposures listed by Standard Industrial Classification or SIC have included e SIC 20 and 21 food beverages and tobacco industry slaughterers and meat packers e SIC 22 23 and 31 textile apparel and leather industry textile winders shoe and leather workers and repairers textile knitting and weaving machine operators e SIC 24 lumber and wood products industry including logging and lumber mill operations most occupations except cabinetmakers e SIC 25 furniture and fixtures industry
90. d against attenuated quite severely by the A network and hardly attenuated at all by the C network Sound levels dB measured using these weighting scales are designated by the appropriate letter i e dBA or dBC The A weighted sound level measurement is thought to provide a rating of industrial noise that indicates the injurious effects such noise has on human hearing and has been adopted by OSHA in its noise standards OTM Driscoll In contrast the Z weighted measurement is an unweighted scale introduced as an international standard in 2003 which provides a flat response across the entire frequency spectrum from 10 Hz to 20 000 Hz The C weighted scale is used as an alternative to the Z weighted measurement on older sound level meters on which Z weighting is not an option particularly for characterizing low frequency sounds capable of inducing vibrations in buildings or other structures A previous B weighted scale is no longer used The networks evolved from experiments designed to determine the response of the human ear to sound reported in 1933 by a pair of investigators named Fletcher and Munson Their study presented a 1 000 Hz reference tone and a test tone alternately to the test subjects young men who were asked to adjust the level of the test tone until it sounded as loud as the reference tone The results of these experiments yielded the frequently cited Fletcher Munson or equal loudness contours which are displayed in F
91. d fields are categorized as near field or far field a distinction that is important to the reliability of measurements The near field is the space immediately around the noise source sometimes defined as within the wavelength of the lowest frequency component e g a little more than 4 feet for a 25 Hz tone about 1 foot for a 1 000 Hz tone and less than 7 inches for a 2 000 Hz tone Sound pressure measurements obtained with standard instruments within the near field are not reliable because small changes in position can result in big differences in the readings The far field is the space outside the near field meaning that the far field begins at a point at least one wavelength distance from the noise source Standard sound level meters i e type I and type ID are reliable in this field but the measurements are influenced by whether the noise is simply originating from a source free field or being reflected back from surrounding surfaces reverberant field A free field is a region in which there are no reflected sound waves In a free field sound radiates into space from a source uniformly in all directions The sound pressure produced by the source is the same in every direction at equal distances from the point source As a principle of physics the sound pressure level decreases 6 dB on a Z weighted i e unweighted scale each time the distance from the point source is doubled This is a common way of expressing the inverse square
92. d level meters that are set to integrate or average sound over a period of time do not use either the fast or slow time constant they will sample many times per second Section III Chapter 5 Page 52 3 Octave Band Analyzer Most sounds are not a pure tone but rather a mix of several frequencies The frequency of a sound influences the extent to which different materials attenuate that sound Knowing the component frequencies of the sound can help determine the materials and designs that will provide the greatest noise reduction Therefore octave band analyzers can be used to help determine the feasibility of controls for individual noise sources for abatement purposes and to evaluate whether hearing protectors provide adequate protection i Octave Band Analyzer Types and Performance Octave band analyzers segment noise into its component parts The standard octave band filter set provides filters with the following center frequencies 16 31 5 63 125 250 500 1 000 2 000 4 000 8 000 and 16 000 Hz The special signature of a given noise can be obtained by taking sound level meter readings at each of these settings assuming that the noise is fairly constant over time The results may identify the octave bands that contain the majority of the total radiated sound power Figure 19 For octave band analysis the ideal sound level meter network weighting scale setting is one that provides no weighting at all such as the Z weighted
93. different devices or materials Here the user should investigate whether alternative and quieter ways exist to accomplish the task or intended service Where practical examples of source substitution include e Using belt drives over gears e Using belt conveyors instead of rollers e Employing mechanical parts ejectors or pickups over compressed air e Substituting quiet air nozzles for open ended pipe or air lines e Replacing omnidirectional fans on electric motors with unidirectional aerodynamic fans e Substituting metal or steel parts with materials having high internal damping properties such as wood nylon or stiff plastic components e Using perforated or mesh panels in place of solid panels Relocation of the Source Controlling noise by locating or relocating the source should be considered for the design and equipment layout of new plant areas and for reconfiguring existing production areas A simple rule to follow is to keep machines processes and work areas of approximately equal noise level together and separate particularly noisy and quiet areas by buffer zones having intermediate noise levels In addition a single noisy machine should not be placed in a relatively quiet populated area Reasonable attention to equipment layout from an acoustical standpoint will not eliminate all noise problems but it will help minimize the overall background noise level and provide more favorable working conditions Here are some exam
94. duction capability of all hearing protectors on the hearing protector package This measure is referred to as the noise reduction rating NRR It is a laboratory derived numerical estimate of the attenuation achieved by the protector It became evident that the amount of protection users were receiving in the workplace with the prescribed hearing protectors did not correlate with the attenuation indicated by the NRR OSHA acknowledged that in most cases this number overstated the protection afforded to workers and required the application for certain circumstances of a safety factor of 50 to the NRR above and beyond the 7 dB subtraction called for when using A weighted measurements For example consider a worker who is exposed to 98 dBA for 8 hours and whose hearing protectors have an NRR of 25 dB We can estimate the worker s resultant exposure using the 50 safety factor The worker s resultant exposure is 89 dBA in this case The 50 safety factor adjusts labeled NRR values for workplace conditions and is used when considering whether engineering controls are to be implemented Estimated dBA exposure 98 dBA 25 7 x 50 89 dBA However when assessing the adequacy of the hearing protection for hearing conservation HC purposes CSHOs should only subtract 7dB from the NRR Exposure for PPE HC enforcement 98 dBA 25 7 80 dBA Single Double Hearing Protection Dual hearing protection involves wearing two forms of hearing pro
95. e for Occupational Safety and Health NIOSH 2009 A technique for estimating the sound power level radiated by pneumatic rock drills and the evaluation of a CSIR prototype rock drill with engineering noise controls National Institute for Occupational Safety and Health NIOSH 1979 Industrial Noise Control Manual document number 79 117a National Institute for Occupational Safety and Health NIOSH No date Heavy construction equipment noise study using dosimetry and time motion studies National Institute for Occupational Safety and Health Section II Chapter 5 Page 103 North Carolina Department of Labor 2000 Occupational Safety and Health Division Field Operations Manual Chapter XV Industrial Hygiene Compliance North Carolina OSHA February OSHA IMIS 2007 Integrated Management and Information System Noise Exposure records 1997 2006 OSHA 2001 Regional Instruction Region II Directive Number STD 1 4 1A Effective Date July 19 2001 Subject Enforcement of the Occupational Noise Exposure Standards 29 CFR 1910 95 1926 52 and 1926 101 Inspection Procedures and Interpretive Guidance Appendix C Economic Feasibility of Noise Control Engineering and Table C 2 Noise Control Engineering Cost Assumptions OSHA 2000 Technical Manual Occupational Safety and Health Administration OSHA 2011 Meeting Summary Stakeholder Meeting on Preventing Occupational Hearing Loss OSHA No date Occupational Noise Exposu
96. e immediately but a little practice is needed to change the battery quickly on some equipment Be prepared so that a low battery doesn t slow you down during an early morning calibration session Noise measurements collected by CSHOs cannot be used as a basis for citations unless they are obtained using equipment that has a current within the past 12 months periodic calibration certificate on file and that has received documented calibration before and after the measurements were made using accepted practices for documentation 2 Sound Level Meters Sound level meters provide instantaneous noise measurements for screening purposes Figure 16 During an initial walkaround a sound level meter helps identify areas with elevated noise levels where full shift noise dosimetry should be performed Sound level meters are useful for e Spot checking noise dosimeter performance e Determining a worker s noise dose whenever a noise dosimeter is unavailable or inappropriate e Identifying and evaluating individual noise sources for abatement purposes e Aiding in engineering control feasibility analysis for individual noise sources being considered for abatement e Evaluating the suitability of HPDs for the actual noise level in an area Section III Chapter 5 Page 48 Figure 16 Sound Level Meter i Sound Level Meter Types and Performance Sound level meters used by Oregon OSHA meet American National Standards Institute
97. e less than 10 dB For age 30 the shifts were 9 dB 10 dB and 8 dB Since the average is less than 10 dB no STS occurred For age 35 all shifts were well above 10 dB so the age correction values will need to be applied Age Correction Values from Table F 1 in Appendix F of 1910 95 2 000 13 000 4 000 Hz Hz Hz Age 20 ms SSS Co _ Difference in age correction values right ear Section III Chapter 5 Page 160 Age Corrected Threshold Shift age 35 right ear Threshold shifts from baseline i Difference in age correction vies 2 e Age corrected threshold sift f3 p fo The age corrected standard threshold shift for the right ear is 13 9 10 3 10 66 The STS occurred at age 35 The audiogram for age 35 should be adopted as the revised baseline Section III Chapter 5 Page 161 APPENDIX K Three Ways to Jump Start a Noise Control Program This presentation provides practical suggestions for reducing excessive noise from three sources The following slides are an excerpt from a presentation by Dennis Driscoll P E during a course held at the 2011 Professional Conference on Industrial Hygiene The slides are reprinted here with the author s permission 1 Pneumatic or compressed air sources 2 Elevated sound levels from sources that can be reduced through maintenance for noise control 3 Machinery noise sources that can be controlled by considering noise while improving machine guarding Thes
98. e parts of the machine or process that are the major contributors to overall noise levels by following these gradients Thus these are the most important to address with appropriate controls It might just take tightening some bolts or installing a new dampening gasket to significantly reduce the noise b Ask workers periodically during sampling if this is a typical work day for noise exposure Note If the CSHO finds out it is a light day for noise exposure and no overexposure exists he or she might need to come back another day to sample If workers are not at their workstations when you do your checks it is important to follow up and determine where they were and what they were doing for that part of the shift and ask whether it is unusual for them to work elsewhere c Include a brief description of the machine and or process contributing to the noise levels i Record octave band analysis readings only if they have significant identified noise source s e g exposures gt 132 dose so this information can be provided to the employer to assist in determining the type of engineering controls Section III Chapter 5 Page 147 Try to have a company representative accompany you during the data collection part of the inspection It is an opportunity to present the findings in a hands on manner on the plant floor almost like a hands on pre closing conference It reduces confusion at the closing and misunderstanding of the citations
99. e situations shown in Table A 2 illustrate the relationship between criterion level threshold and exchange rate and show the importance of using a dosimeter with an 80 dBA threshold to characterize a worker s noise exposure For example an instrument with a 90 dBA threshold will not capture any noise below that level and will thus give a readout of 0 even if the worker being measured is actually being exposed to 89 dBA for 8 hours 1 e to 87 of the allowable noise dose over any 8 hour period Table A 2 Effect of Threshold Settings on Dosimeter Readout Dosimeter With Threshold Set at 80 dBA Dosime ten ivath Exposure Conditions Threshold Set at 90 dBA percent of measured dose 90 dBA for 8 hours 100 0 100 0 89 dBA for 8 hours 87 0 percent of measured dose Assumes 5 dB exchange rate 90 dBA PEL ideal threshold activation and continuous sound levels Time weighted average TWA A constant sound level lasting 8 hours that would result in the equivalent sound energy as the noise that was sampled TWA always averages the sampled sound over an 8 hour period This average starts at zero and grows It is less than the Lay for a duration of less than 8 hours is exactly equal to the Lay at 8 hours and grows higher than the Lavg after 8 hours Example Think of a TWA as having a large 8 hour container that stores sound energy If you run a dosimeter for 2 hours your Lavg is the average level for those 2 hours consider t
100. e three sources are some of the most frequent causes of excessive workplace noise Controlling these sources can have a marked impact on the overall noise exposure levels that workers experience Additionally these three items will provide the greatest noise reduction per dollar invested and can even have an economic payback through energy savings and life expectancy of equipment The Economics of Noise Control Engineering Versus the Hearing Conservation Program A Few Key Steps to Jump Start Your Noise Control Program Success builds success Section III Chapter 5 Page 162 Impediments and Road Blocks Lack of time background money and or confidence to get started Resistance indifference and or lukewarm support from above Resistance indifference and or lukewarm support from below operators mechanics Impediments and Road Blocks Let s look at three 3 homeruns we can all manage 1 Pneumatic or compressed air sources 2 Maintenance for noise control and 3 Improving machine guarding These three items will provide the greatest noise reduction per dollar invested and can even have a payback in dollars through energy savings and life expectancy of equipment Section III Chapter 5 Page 163 Pneumatic and Compressed Air Systems She Pneumatic and Compressed Air Systems The usage of compressed air is often a plant wide noise issue in manufacturing plants Compressed air can easily be re
101. easured in air in dB as opposed to 8 hour TWAs or ceiling values measured in water in dB Though ultrasonic frequencies are not audible to the human ear it is clear that the international community is concerned about the effects that subharmonic frequencies have on human health Section III Chapter 5 Page 125 Table C 2 Examples of International Occupational Exposure Sound Pressure Level Ceiling Limits in dB for 1 3 Octave Bands Decibel Limits Proposed By Japan USSR Sweden ACGIH 1971 1975 1978 2003 Adapted from Health Canada 2008 Guidelines for the Safe Use of Ultrasound Part II Industrial amp Commercial Applications Safety Code 24 For a detailed review of ultrasound effects on human hearing published literature international ultrasound standards and recommendations for future directions see Lawton B W 2001 Damage to Human Hearing by Airborne Sound of Very High Frequency or Ultrasonic Frequency Health and Safety Executive The report concludes There is not sufficient data in the literature to support or even contemplate a dose response relation between occupational exposure to VHF noise and resultant hearing risk Section III Chapter 5 Page 126 APPENDIX D Combined Exposure to Noise and Ototoxic Substances Ototoxic substances came gradually to the attention of occupational health and safety professionals in the 1970s when the ototoxicity of several industrial chemic
102. ect VIEW SET PARAMETERS Press key to VIEW SET PARAMETERS Make sure RESPONSE is SLOW EXCHANGE RATE IS 5 dB CRITERION LEVEL IS 90dB CRITERION TIME IS 8 hr and THRESHOLD is 80 dB Press the On Off ESC key three times to exit Now repeat the steps above for DOSE2 which should be set up for OSHA PEL The only difference is for the PARAMETERS where the THRESHOLD should be set for 90 dB Press the On Off ESC key three times to exit Pre Calibrate 6 T7 Turn on calibrator and check LOBAT indicator Replace batteries if needed Insert unit s microphone remove windscreen into calibrator using Quest adapter 053 884 From the START menu press and release CAL softkey and the CAL screen appears With CALIBRATE highlighted press key and the PRE CALIBRATION screen appears Note If POST CALIBRATION screen appears the data has not been cleared from the NoisePro If required use the A V arrow keys to adjust the displayed value to match the calibrator output Press key to save store the calibration Unit will perform self calibration and return to CAL screen Section II Chapter 5 Page 153 9 Document Pre calibration on OSHA 92 form 10 Press and release the On Off ESC key to return to START screen Collect Data 11 Clip microphone with windscreen attached to the top of the shoulder away from the 2 neck Clip meter onto individual s belt on the side opposite the microphone Try to run the microphone
103. ed from the Buy Quiet Purchasing tab in the top navigation menu Other NASA hearing conservation resources such as the Auditory Demonstrations series and TWA Calculator are also part of this website All are available as free publicly accessible digital downloadable files This site is hosted and maintained by Nelson Acoustics as a service to the noise control and hearing conservation technical community and was updated in 2012 The website describes itself as follows The Roadmap guides users through a stepwise process that includes project planning researching the marketplace selecting an achievable noise emission criterion and developing a specification document The Roadmap also includes guidelines for identifying the appropriate government procurement strategy for each purchase based on an assessment of the purchase specific long term financial and noise exposure risk The Roadmap is applicable to both public and private sector organizations and the downloadable forms and worksheets can be customized to each organization There is a very brief tutorial PowerPoint presentation here F Cost of Hearing Loss Cost of Hearing Conservation Programs Nelson D A 2012 White Paper The Long Term Cost of Noise Exposure NASA s Roadmap see entry in the previous section includes this paper which provides one alternative methodology for calculating the cost of long term exposure to the noise emission of various products being considered
104. een 3 000 Hz and 4 000 Hz are the earliest to be affected by exposure to noise Audiograms often display a 4 000 Hz Notch in patients who are developing the beginning stages of sensorineural hearing loss 3 Speed The speed at which sound travels c is determined primarily by the density and the compressibility of the medium through which it is traveling The speed of sound is typically measured in meters per second or feet per second Speed increases as the density of the medium increases and its elasticity decreases For example e In air the speed of sound is approximately 344 meters per second 1 130 feet per second at standard temperature and pressure e In liquids and solids the speed of sound is much higher The speed of sound is about 1 500 meters per second in water and 5 000 meters per second in steel The frequency wavelength and speed of a sound wave are related by the equation c f Where c speed of sound in meters or feet per second f frequency in Hz and wavelength in meters or feet 4 Sound Pressure The vibrations associated with sound are detected as slight variations in pressure The range of sound pressures perceived as sound is extremely large beginning with a very weak pressure causing faint sounds and increasing to noise so loud that it causes pain The threshold of hearing is the quietest sound that can typically be heard by a young person with undamaged hearing This varies somewhat among indi
105. eld In other words it decreases by less than 6 dB each time the distance from the sound source doubles Far from the noise source unless the boundaries are very absorbing the reflected sound dominates This region is called the reverberant field If the sound pressure levels in a reverberant field are uniform throughout the room and the sound waves travel in all directions with equal probability the sound is said to be diffuse In actual practice however perfectly free fields and reverberant fields rarely exist most sound fields are something in between 7 Sound Power Up to this point this discussion has focused on sound pressure Sound power however is an equally important concept Sound power usually measured in watts is the amount of energy per unit of time that radiates from a source in the form of an acoustic wave Generally sound power cannot be measured directly but modern instruments make it possible to measure the output at a point that is a known distance from the source Understanding the relationship between sound pressure and sound power is essential to predicting what noise problems will be created when particular sound sources are placed in working environments An important consideration might be how close workers will be working to the source of sound As a general rule doubling the sound power increases the noise level by 3 dB As sound power radiates from a point source in free space it is distributed over a
106. ense as they are one size devices designed to fit nearly all adult users Earmuffs are designed to cover the external ear and thus reduce the amount of sound reaching the inner ear Care must be taken to ensure that the seal of the earmuff is not broken by safety glasses facial hair respirators or other equipment as even a very small leak in the seal can destroy the effectiveness of the earmuff Earmuffs should be chosen based on the frequency that needs to be reduced Refer to the EPA label on the manufacturer s product Earmuffs are a good choice for intermittent exposure given how easy they are to put on and take off Additionally in cold environments their warming effect is appreciated OTM Driscoll Hearing bands are a third type of HPD Figure 11 and are similar to earplugs but with a stiff band that connects the portions that insert into a worker s ears The band typically wraps around the back of the wearer s neck though variations are available Hearing bands come in a variety of sizes shapes and materials and are popular for their convenience Hearing bands may not provide the same noise attenuation as properly fitting earplugs as the portions that fit into the ears are stationary and cannot be twisted into place like earplugs Earplugs earmuffs or hearing bands alone might not provide sufficient protection from significantly high noise levels In this case workers should wear double hearing protection earmuffs with earplugs A
107. ense materials such as carpet and fiberglass Painting concrete creates a smooth surface that greatly increases the percentage of sound that is reflected at all frequencies Table V 2 Absorption Coefficients of Common Surface Materials and Finishes Carpet heawyon concrete 002 oos om 037 o0 os Carpet heavy on 40 oz hairfelt 0 08 0 24 0 57 071 0 73 or foam rubber pad Carpet 40 oz per square yard with latex backing over felt or foam rubber pad of same density on concrete 0 27 0 36 0 34 0 48 Fabric light velour 10 0z square yard hung straight in contact 0 03 0 04 0 11 0 17 0 24 0 35 with wall Fabric medium velour 14 Pp ee ee 0 14 035 055 0 72 0 72 0 65 square yard draped in half Section II Chapter 5 Page 81 Floors linoleum asphalt vinyl rubber or cork tile on concrete Floors wood parquet in asphalt on concrete 0 07 Glass large panes of heavy plate glass 0 04 0 03 0 02 Glass ordinary window glass 035 O 0 07 Gypsum board 1 2 inch nailed to 2x4 wood frame 16 inches on 0 10 0 05 0 04 0 07 center C meore oo oor oor om om om Opening covered by grill e g ventilating 0 25 0 75 Plaster gypsum or lime smooth finish on tile or brick Plaster gypsum or lime rough finish on lath Plywood paneling 3 8 inch thick Malet aa endo 0 015 0 020 0 025 swimming pool Fiberglass boards and blankets 2 inches thick 1 5 to 3 pounds per square fo
108. equired when you find that measured noise levels approach 85 dBA and any other time that you suspect that noise levels are elevated Use hearing protection anywhere it is noisy enough that you would have to raise your voice to carry on a conversation with someone 3 feet away In some situations double hearing protection might be necessary see Oregon OSHA s Policy amp Procedure 28 P amp P 28 Personal Protective Equipment Policy for OR OSHA Staff B Reviewing Employer Records Review employer records to determine whether hazardous noise levels have been found in the past and to evaluate the employer s hearing conservation and recordkeeping programs The records can also indicate what steps the employer has taken to reduce any excessive noise exposure and whether there is evidence that workers are experiencing noise induced hearing Section III Chapter 5 Page 64 loss Also ask the employer for noise questionnaires that may be in use Refer to Oregon OSHA s Program Directive PD 266 OR OSHA Access to Employee Medical Records 2 11 09 for guidance on appropriately requesting reviewing documenting and retaining worker audiogram records If you can conduct the walkaround inspection before the records review review the employer s records while noise dosimeters are operating Periodically return to the work area to confirm that the equipment is still operating properly and to collect sound level measurements to compare
109. equired frequencies so the average will be greater than 10 dB The difference in hearing thresholds between the current and baseline audiograms is 11 13 and 11 2008 Section III Chapter 5 Page 156 dB at 2 000 3 000 and 4000 Hz respectively It is now necessary to apply the age correction values from Table F 1 in Appendix F of 1910 95 Age Correction Values for Males from Table F 1 in Appendix F of 4 7 sf Ts e __ Age Corrected Threshold Shift Right Ear Threshold shifts from baseline s Age corrected threshold shift Since all age corrected changes in hearing threshold are less than 10 the average will be less than 10 No STS has occurred Example 2 A 50 year old female worker with 10 years of service has the following audiometric data Test Frequency Left Ear Hz Test Frequency Right Ear Hz s b b a The average threshold shift for the left ear is 10 10 8 3 9 33 Since the average for the left ear is less than 10 no STS has occurred The average threshold shift for the right ear is 9 12 16 3 12 33 the age correction values must be applied to determine whether an STS has occurred Age Correction Values for Females from Table F 1 in Appendix F of 1910 95 Age 40 baseline Difference in age correction 3 3 values Section IH Chapter 5 Page 157 Age Corrected Threshold Shift current year age 50 Test Frequency Left Ear Hz 4 oo h he o Age cor
110. er at 7 00 a m and pause for lunch at 12 00 p m Start run again at 12 30 p m and stop at 3 30 p m There are two studies in the same session Example 2 A worker performs three different job tasks throughout an 8 hour shift The CSHO wants to know the respective exposure levels for each task so the dosimeter is paused after each task and the data is recorded There are three studies in the same session Record the data on a Quest dosimeter readout worksheet and complete the lower portion of the OSHA 92 form Dosimeter Data and Exposure Summary sections Section III Chapter 5 Page 154 Post Calibrate Instrument 20 From the start screen press and release CAL soft key the CAL screen appears with CALIBRATE highlighted Turn on the calibrator and insert the unit s microphone into the calibrator using appropriate adapter Press key and the POST CALIBRATION screen appears Note In a POST CALIBRATION you are not allowed to adjust the SPL value Press key to save store the POST CABLIBRATION value The CAL screen will show the most recent PRE and POST calibrations that have been performed 21 Document Post calibration on OSHA 92 form Turn Off 22 Turn off unit by pressing and holding On Off ESC key until the display counts down from 5 and then shows a black box and shuts off SUMMARY of OSHA NOISE REQUIREMENTS OSHA Noise Limits Dose to Determine OSHA 92 Noncompliance Codes Hearing Conservation Program En
111. ers compensation insurance rates purchase of hearing aids purchase of HPDs and the various costs of administering a hearing conservation program Differences in how inflation is adjusted also create notable variations in both the costs of noise exposure and expenses related to purchasing installing and maintaining engineering controls Section II Chapter 5 Page 93 In 2001 OSHA Region HI produced an instruction on conducting economic feasibility evaluations for noise control engineering This instruction was based in part on information published in the Regulatory Impact and Regulatory Flexibility Analysis of the Hearing Conservation Amendment OSHA Office of Regulatory Analysis February 1983 More recently several sources have offered more detailed methods for evaluating the costs of noise and benefits of noise control described in Appendix G The rest of this section presents information adapted from the Federal OSHA Region III 2001 instruction mentioned above Directive Number STD 1 4 1A The assumptions and tables in this section contain examples of approximate costs and other related information This information is used here to demonstrate through examples some simple methods that CSHOs can use when considering economic feasibility of engineering controls compared to a hearing conservation program The numbers used in these assumptions tables and examples should be refined as appropriate for each inspection and locality
112. est way to reduce this noise level was to apply a damping compound to the feeder bowl The damping compound reduced the noise level 12 dBA to 89 dBA Five gallons of the compound cost 180 to 250 plus the approximate labor cost of 27 per hour and 1 hour per bowl iii Design Case study A company used a tungsten carbide tipped blade to cut aluminum The blade produced an average noise level of 97 dBA the company reduced this noise level to 91 dBA by replacing it The original blade was 350 mm in diameter with 84 teeth and a thickness of 3 5 mm the new blade was also 350 mm in diameter but had 108 teeth and a thickness of 3 2 mm The former blade cost between 10 and 40 whereas the blade with more teeth cost between 60 and 400 Government of Western Australia 2009 Case study A company designed a bulldozer whose engine ran at a rated speed 5 lower than a typical bulldozer The bulldozer also included other noise reduction measures such as a cab damper mount At 15 meters from the newly designed bulldozer the noise level is 10 dB lower than a typical bulldozer 60 dB vs 70 dB The bulldozer operator s exposure was 7 dB lower than with the previous design The costs of the old and new designs are difficult to compare but range from 70 000 for a 1990 version of the old design to 235 000 for the new design Case study A U S government agency recognized that it had been spending money on retrofit noise controls while still buying new
113. et is split into two both identical to the original One signal is fed to the worker s headset and the other is fed to the similar headset the monitoring headset The monitoring headset is placed on the HATS so that it is being worn in the same manner as the worker s headset The signal measured from the HATS ear is fed to a set of electrical filters an audio equalizer that carries out the HATS eardrum to diffuse field transfer function The output from the electrical filters is then fed to a noise dosimeter The dosimeter reads the noise exposure dose in percentage The percentage dose can be then calculated to a time weighted average TWA noise exposure level in dBA Section III Chapter 5 Page 134 The term diffuse field refers to sound that comes from all directions such as from a source and also many sound reflecting surfaces reverberant sound Most factory production rooms are diffuse fields In contrast a free field is a space with no echo or reflected sound such as a location outdoors away from any structures In a free field all sound comes from a single direction the point where the sound source is located Note that the monitoring headset must be acquired before sampling can begin It should be identical in brand and model to the headset worn by the worker Both the worker s and the monitoring headsets should be characterized i e frequency response and sensitivity and recorded After the TWA level is calculated
114. et the ceiling values assuming that the worker has no direct contact with the ultrasound source but that the worker does have contact with water or other media that can transfer the sound waves For additional information on ultrasound exposure levels ceiling values and 8 hour TWAs that apply to other frequencies as well as ceiling values measured underwater refer to the complete ACGIH TLV for ultrasound see ACGIH 2012 Threshold Limit Values for Chemical Substances and Physical Agents amp Biological Exposure Indices American Conference of Governmental Industrial Hygienists C 2 Controls High frequency noise is highly directional and is associated with short wavelengths This means that it is easily reflected or blocked by any type of barrier The wavelength of a 16 kHz tone for example is about 3 4 inch A modest barrier extending just 1 to 2 inches beyond the source is generally sufficient to reflect noise of approximately the same frequency away from a nearby worker High frequency audible noise is also easily absorbed by many acoustical materials such as glass fiber or foam C 3 International Ultrasound Exposure Limit Recommendations Over the past decades several countries have set exposure limits or recommended levels for ultrasound at various frequencies The differences in limits are great and reflect differences in the interpretation and analysis of studies on ultrasound and human health Table C 2 lists ceiling values m
115. evels exceed the PEL an octave band analyzer can help you determine the frequency profile of the sound This information can aid in pinpointing the cause of the sound e g slipping belt vibrating supports and will be useful for planning control measures The sound level meter is also useful for confirming the extent to which the employer s noise reduction measures have reduced workers noise exposure In this case octave band analysis can help confirm that the materials used are appropriate for controlling the particular noise When monitoring is complete at the end of the day follow standard procedures for recording results from the instruments If necessary consult the instrument user s manual or contact CTC for assistance Dosimeter output usually includes the TWA normalized to 8 hours the Layg or Leg representing the average dose for the period monitored the percent dose and the maximum or peak reading Do not neglect to perform the post use calibration check on each instrument Section III Chapter 5 Page 69 D Follow Up Monitoring If noise levels documented by sound level meter or dosimetry on the first day indicate that additional sampling is required you will need to return to conduct follow up monitoring The additional monitoring could be necessary to confirm that workers are adequately protected or that an overexposure exists or you might need to monitor another operation not being performed on the first day Since the f
116. ever animal data clearly show an effect Further human studies are needed for clarification of these issues However in the interim one cannot rule out a likely relationship between solvent exposure and hearing impairments Overall in combined exposure to noise and organic solvents interactive effects may be observed depending on the parameters of noise intensity impulsiveness and the solvent exposure concentrations In cases of concomitant exposures animal studies suggest that solvents might exacerbate noise induced impairments even though the noise intensity is below the permissible limit value The text in this appendix is adapted from a comprehensive review of solvent noise interaction published as European Agency for Safety and Health 2009 Combined Exposure to Noise and Ototoxic Substances Reproduction of this report is authorized provided the source is acknowledged Other useful review articles on solvent noise interactions Campo P 2000 Noise and Solvent Alcohol and Solvent Two Dangerous Interactions on Auditory Function Kim J 2005 Combined Effects of Noise and Mixed Solvents Exposure on the Hearing Function Among Workers in the Aviation Industry Introduction includes a good overview of other studies on the same topic Volpin A 2006 Interactions Between Solvents and Noise State of the Art Link is to abstract Section III Chapter 5 Page 129 References Cited in This
117. excessive noise from the impact of metal on metal When the chute is coated with a damping material e g mastic asphalted felt the noise level is reduced Figure 31 shows a steel plate covering a moving part on a piece of equipment A sheet of plastic foil is placed between the two steel plates providing a damping effect Figure 31 Damping Effect Damping is typically used to dissipate energy associated with large thin vibrating panels on pieces of equipment For low frequency noise significant reductions in noise levels can occur when only 50 of the surface area of the vibrating panels is treated with damping material It is necessary to treat the entire panel with damping material in order to achieve similar reductions in high frequency noise Section II Chapter 5 Page 75 Damping materials fall into three major categories free layer constrained layer and constrained layer laminates Simple free layer damping materials consist of rubbery viscoelastic materials that can be painted sprayed troweled or adhered i e with adhesive or magnetism onto the noisy surface Typically on sheet metal a layer of damping material half the thickness of the metal or 10 by weight will eliminate the ringing from impact A much thicker layer of damping material two to three times the thickness of the metal will increase the sound absorption coefficient of the metal to approximately 0 3 to 0 6 Constrained layer damping ma
118. expectancy of 10 years so the average cost per year is 1 000 b A second engineering option is to enclose the existing planer with a plywood shop built structure lined with sound absorbing fiberglass this design has no production penalty and a life expectancy of 10 years Three workers will work together for 10 hours to install the enclosure for a total of 30 hours This option reduces the workers exposure to a similar extent as would modifying the planer as described above From Table V 6 we select the lower cost of 4 000 as the enclosure can be fabricated in plant Table V 6 also indicates that the enclosure will have a 5 maintenance cost Table V 6 indicates that the labor rate is 27 per hour so the total cost will be the cost of control maintenance at 5 over 10 years installation labor thus 4 000 2 000 810 6 810 total assumed cost Per Assumption 1 this engineering control has a life expectancy of 10 years so the average cost per year is 6 810 10 681 Considering that all 100 workers will benefit from the implementation of this engineering control the assumed cost for hearing conservation is calculated from Table V 5 with a 5 increase in the cost of the hearing conservation program based on 100 workers participating 375 x 05 375 394 per worker per year 394 x 100 workers 39 400 per year for all 100 workers Given that the engineering option cost per year is less than the cost per yea
119. f noise reduction materials Transmission loss is the difference in sound power level across the noise reduction material It is the difference between measurements made on either side of the material 3 Receiver Treatment i Enclosures Cabs Control Rooms Isolation Booths The receiver again the worker can be protected from noise by an isolation booth In the construction industry a common example of a personnel enclosure is the cab on heavy equipment such as a dozer Figure 42 shows another type of personnel enclosure in this case a multi person control room The design concepts for personnel enclosures are similar to those for equipment enclosures but because they are used to enclose people safe access and egress fresh air supply and thermal comfort are critical considerations For any personnel enclosure the room or booth s ability to exclude noise is impaired while the door is open Workers are more likely to keep the door closed if they perceive that the atmosphere inside the booth is at least as comfortable as it is outside the booth Workers generally use a personnel enclosure most effectively keeping the door closed to exclude noise when the enclosure provides tempered air seasonally heated or air conditioned and a sense of air movement inside Figure 42 Personnel Enclosure Driscoll Principles of Noise Control Section III Chapter 5 Page 89 B Engineering Controls and Economic Feasibility 1 Overview
120. ff guns or air wands These tools come in a variety of sizes and shapes and can generate noise levels of 90 dBA to 115 dBA depending on the velocity of the air and the surface area they contact It is recommended that the Noise and Vibration Control Product Manufacturer Guide be consulted for a list of available suppliers Usually the manufacturer websites provide sufficient information and self help guidance to enable selection of the most appropriate device for retrofit It should be noted that silencers for pneumatic or compressed air systems normally require routine inspection maintenance and or replacement as these silencers will plug up with debris be removed by operators or occasionally become damaged over time If these devices are kept in good working order however excessive high velocity air noise in manufacturing facilities technically should not be an issue The major problem with air guns is that like other pneumatic or compressed air systems used to drive and motivate machinery equipment operators will often increase the air pressure in an attempt to create more blow off power Earlier in the High Velocity Air Flow section it was noted that the intensity of noise is proportional to the 8th power of the air velocity Consequently a higher pressure setting will significantly increase the noise level In addition when a compressed air silencer is installed on machines many operators will remove or suppress this device to maintai
121. for a particular purchase This allows the comparison of the true cost of candidate products that may differ in noise emission and price Users may input their own experience for example as discussed in Appendix G of Section III Chapter 5 Page 109 this chapter hearing conservation costs vary widely due to factors such as economies of scale geography and what elements are included in the calculation NASA seeks feedback on this methodology in order to continue to improve and update the Roadmap Driscoll D P and L H Royster 2003 Chapter 9 Noise Control Engineering In American Industrial Hygiene Association The Noise Manual 5th edition Edited by E H Berger et al Fairfax VA American Industrial Hygiene Association See Benefits and Costs of Noise Control on pages 281 289 Acoustical Consultants National Council of Acoustical Consultants 2012 What Sets an Expert Apart This site also includes an online directory of consultants National Aeronautics and Space Administration No date When to Hire an Acoustical Consultant Get Help Before You Get in Over Your Head This Web page part of NASA s Roadmap lists examples of situations where an acoustical engineer can provide valuable expertise and when a product representative can be useful The site also describes credentials that acoustical professionals might have American Industrial Hygiene Association Search for a Consultant Industrial hygiene professional
122. from the measurement add to the result the sensitivity difference between the worker s and the monitoring headsets Example TWA from the measurement 73 dBA Sensitivity difference worker s headset sensitivity monitoring headset sensitivity 3 dB Worker s daily noise exposure level 73 3 70 dBA Contact the Oregon OSHA Laboratory for more information F 3 Acoustic Limited Devices Laboratory evaluations have determined that headsets can be categorized in two basic groups Those without any form of electronic limiting device Those with some form of limiting device built into the headset Most modern telecommunication headsets use sophisticated limiting circuits Some personal audio headsets e g for MP3 players also have this capability Headsets with acoustic limiting devices that are functioning as designed have been shown in both laboratory and field tests to provide enough protection to keep worker noise exposures below OSHA permissible noise levels In some work environments however headsets without limiting devices have caused worker noise exposures to exceed the levels permitted by OSHA For more information see OSHA s letter of interpretation dated 4 14 1987 Use of Walkman Radio Tape or CD Players and Their Effect When Hearing Protection is in Use Section II Chapter 5 Page 135 APPENDIX G Alternatives for Evaluating Benefits and Costs of Noise Control General Guidelines General guideline 1 Most
123. ft Test Frequency Right Ear Hz Ear Hz Age Corrected Threshold Shift current year age 40 Section III Chapter 5 Page 159 In scanning the data for the left ear the average threshold shift will exceed 10 dB but not 25 dB An STS has occurred but not an OSHA recordable case The average STS is 19 20 19 3 19 33 dB Likewise for the right ear the average shift will be greater than 10 dB but less than 25 dB An STS has occurred for the right ear but not an OSHA recordable case The average is 16 15 11 3 14 Since the STS is much larger than 10 dB for both ears it is prudent to examine data from the intervening years to determine when the STS occurred In scanning the data for age 30 for the left ear none of the shifts exceed 10 dB before age correction so the STS did not occur at that interval In scanning the data for age 35 the shifts were 12 dB 14 dB and 11 dB The age correction values will need to be applied Age Correction Values from Table F 1 in Appendix F of 1910 95 2 000 13 000 14 000 Hz Hz Hz E a Difference in age correction values left ear o OE Test Frequency Left Ear Hz o y y po pw pow The average age corrected threshold shift at age 35 for the left ear was 10 11 7 3 9 33 No STS occurred in that interval There is no need to adopt a revised baseline for that interval For the right ear review data for the intervening years to determine when the STS occurred For age 25 all shifts wer
124. g Extracted from BLS Table SNRO8 published in 2010 Figure 24 Navigating to IMIS Noise Citations UNITED STATES DEPARTMENT OF LABOR opu INLA Quit Q Occupational Safety amp Heath Administration We Cn Help Gooey aol Seto Came net EA rs A Joe Sta As Os Deane Ma btreet trist ceca Bo eet beet oo ee ee mipun Rew riin Iso Feta M piman a Ao term om 500 6 Faid pron A AD ed ODE Ee d D PAT Jg E thet ore d Ayr ot amp gaa Pe a ard Oth Pe agea a bene rant he et wert Pe et d he Petpet Drees FA UM fee ed wat fen Oe powder gers red Dal esd erates Oe caer D eect Pe tet tat oS Se Bore ced Org OM agare pres 3 ne sine Pe weet M Cetera De nat brpa ad Kesler weet ate Orin Erdara ty a pan SE cnn P SAC onie ty Da irag Me wire SE Ma Ponds Po ately u eer De Bptatete Gen of Oe EE serene Cores h pA arn Genial Arara Ww p qwufed SE eee y a One Nna hara Cotniet rienda te a gedai SK Deemer Me Gag ov r Prag fe a aaae ii IMIS Noise Citations by Industry If the establishment has not been inspected previously OSHA s online records can show you whether the noise and hearing conservation standards are among those frequently cited in this industry or whether the industry is listed as one that receives a lot of noise citations The CSHO can easily search the inspection information database to determine whether previous inspections of that industry or a similar industry resulted in citati
125. g Conservation Program Costs and Corrections Based on Worker Geography Costs per worker are sometimes lower for a large scale hearing conservation program with many workers than for a small program covering just a few people This economy of scale may reduce the per worker cost under some circumstances such as when a fixed daily rate service can serve many workers in one day versus serving just a few workers for the same daily fee Worker geography is a primary reason an employer might encounter this situation Assume that the estimated cost per worker for a larger hearing conservation program will be 375 For smaller hearing conservation programs with workers spread over a wide geographic area adjustments to this cost are made as follows Total Number of Workers at Percent Increase per the Same Geographic Worker per Year Over Location the Unit Cost Ps l o O o SUS 50998 o References for Table V 5 data were adapted from Table 7 in Regulatory Impact and Regulatory Flexibility Analysis of the Hearing Conservation Amendment USDOL OSHA Office of Regulatory Analysis February 1983 The example unit cost 375 worker for a hearing conservation program in 2010 dollars is the midpoint in the cost range of 350 to 400 described in Appendix G 1 2 of this OTM chapter Resulting Calculation per Worker per Year With Unit Cost at 375 Section III Chapter 5 Page 100 Table V 6 Noise Control Engineering Cost Assumptions This table pro
126. g administrative control paragraph however these are deemed economically feasible regardless of the cost Assumption 12 If engineering design for noise controls is done by the employer s engineering or industrial hygiene staff then there will be no additional engineering costs applied to the control In this case the Table V 6 values will determine the costs of an engineering control Assumption 13 If outside or consulting engineering services are required to design and fine tune the control then these costs must be estimated and added to Table V 6 values For cost estimation the hourly rate for a consulting acoustical engineer is assumed to be 150 2010 dollars The daily rate is assumed to be 1 000 Assume that the consulting engineer is local and therefore no travel or per diem costs need be considered For each day in the field it is customary for a consulting engineer to charge one additional day for report plan preparation 3 General Principles An engineering control is any physical alteration in the workplace that will reduce occupational noise exposure An administrative control is any manipulation of the worker s work schedule procedure or practice that will result in a reduction in the daily noise dose 4 Examples The following examples will serve to illustrate how and when economic feasibility determination is necessary Section III Chapter 5 Page 95 i Dusty Foundry There are 100 production workers exposed
127. ge In other words assuming that 100 coverage results in 26 dB of attenuation 50 coverage would provide approximately 23 dB of reduction 25 coverage would produce a 20 dB decrease and so on Next for free layer damping treatments it is recommended that the application material be at least as thick as the panel or base layer to which it is applied For constrained layer damping the damping material again should be the same thickness as the panel however the outer metal constraining layer may be half the thickness of the base layer Finally just because a surface area vibrates it is not safe to assume it is radiating significant noise If fact probably less than 5 of all vibrating panels produce sufficient airborne noise to be of concern in an occupational setting For damping materials to be successful at a minimum the two following conditions must be satisfied determine by a comprehensive noise control survey 1 The panel being treated must be capable of creating high noise levels in the first place 2 The structure must be vibrating at one of its natural frequencies or normal modes of vibration Section III Chapter 5 Page 34 When selecting the right type of damping material it is recommended that the person making the decision refer to the expertise of the product manufacturer or their designated representative s Typically the supplier will need to obtain specific information from the buyer such as the temperature and
128. gineering Controls PEL 90 dBA 100 Dose Ip only Greater than or equal to the indicated dose The permissible exposure limit PEL is also known as the criterion level The criterion level is the continuous equivalent 8 hour A weighted sound level that constitutes 100 of an allowable noise exposure Section II Chapter 5 Page 155 APPENDIX J Reviewing Audiograms Note In the early 1990 s Oregon OSHA adopted most of the Federal Noise standard with a few exceptions One exception was not allowing the use of presbycusis charts age correction factors when evaluating an employee s yearly hearing test to determine if a Standard Threshold Shift has occurred Oregon OSHA will allow the use of age correction charts only when determining that cases should be recorded on the OSHA 300 log see 8 4 2000 Interoffice Memorandum Compare the most recent audiogram with the baseline audiogram If a Standard Threshold Shift STS is observed review data for intervening years to determine when the STS occurred The baseline audiogram is usually but not always the first audiogram If a later audiogram shows lower hearing thresholds that would be the baseline If a persistent STS is identified the audiogram after the STS is identified would be adopted as the revised baseline for future comparisons Evaluate data for each ear separately A threshold shift can occur in one ear and not the other Use threshold data only for the t
129. he day Pre and post calibrations also confirm that changes in temperature or humidity have not affected the instrument s accuracy If practical spot check the instrument with a calibrator after the stabilization period When unpacking a cold instrument in a warm environment or moving from one temperature zone to another allow the instrument at least 5 minutes to stabilize for each 18 F 10 C of change Each instrument model is calibrated in a slightly different manner but the general process follows basic standard steps Typical daily pre use calibration involves 1 setting up the instrument for use 2 turning on both the electronic calibrator and the noise measuring instruments to allow them to warm up 3 checking the calibrator and instrument battery charge 4 testing the instruments with a standard tone of known pitch and intensity produced by the calibrator e g 114 dB at 1 000 Hz 5 checking the instrument reading during the test and making minor adjustments to the instrument if necessary and 6 documenting the calibration results For the post use calibration check the process is repeated without step 5 after the instrument has been used Both the pre and post use calibration must be documented If it isn t properly documented it didn t happen Confirm that you understand the procedures for calibrating each of the instruments you use If in doubt review instructions in each instrument s user s manual and the
130. his a smaller 2 hour container filled with sound energy For TWA take the 2 hour container and pour Section III Chapter 5 Page 116 that energy into the 8 hour container The TWA level will be lower Again TWA is always based on the 8 hour container When measuring using OSHA s guidelines TWA is the proper number to report if the full workshift was measured Type 1 Type 2 or Class 1 and Class 2 Two different accuracy specifications for noise measurements Type 1 measurements are accurate to approximately 1dB and Type 2 measurements are accurate to approximately 2dB The accuracy of the measurements varies however depending on the frequency of the sound being measured Z weighting An unweighted measurement scale that does not apply any attenuation or weighting to any frequency Instead this scale provides a flat response across the entire spectrum from 10 Hz to 20 000 Hz making it useful for octave band analysis and evaluating engineering controls Acknowledgments Dennis Driscoll Raeco 3M Quest Section III Chapter 5 Page 117 APPENDIX B Sample Equations and Calculations B 1 Sound Pressure Level The human ear can hear a broad range of sound pressures Because of this the sound pressure level Lp is measured in decibels dB on a logarithmic scale that compresses the values into a manageable range In contrast direct pressure is measured in pascals Pa Lp is calculated as 10 times the logarithm of the square
131. his control therefore is both economically and technically feasible Section III Chapter 5 Page 97 4 In the finishing department two pedestal grinders were sampled for noise Although both grinders were identical models finishing the same type of castings one operator s exposure was 89 dBA while the other one s was 98 dBA Further investigation revealed that the noisy grinder had defective idler bearings Would bearing replacement be an economically feasible engineering control From Assumption 11 we do not need to do an economic analysis for bearing replacement on this pedestal grinder because the noise is from the defective idle bearings which need to be replaced to keep the equipment in good working order Therefore this control is economically feasible and should be cited as a violation of b 1 5 To abate engineering violations Dusty Foundry must engage a consulting engineer Consider problem 2 b and 2 c above Dusty Foundry will need one day with the engineer on site to evaluate and prepare an abatement report The cost for engineering will be 1 000 x 1 days 1 000 1 000 4 088 cost of controls 5 088 Therefore the total cost for these controls with consulting engineering assistance is 5 088 which is still less than the cost of hearing conservation 9 456 The engineering controls are still economically feasible ii Rocking Chair Furniture Company The company has 100 production workers exposed to dail
132. his exposure level in perspective 29 CFR 1910 1000 Table Z 2 lists OSHA s 8 hour time weighted average permissible exposure limit for styrene as 100 ppm with a 200 ppm peak and up to 600 ppm permitted for no more than 5 minutes in a 3 hour period Section III Chapter 5 Page 183
133. hree required frequencies which are 2 000 3 000 and 4 000 Hz For each audiogram compare to the baseline and take the average of the difference in threshold at the three required frequencies If the average is less than 10 dB no STS has occurred If the average is greater than or equal to 10 dB the age correction values must be applied to determine whether an STS has occurred To apply the age correction values subtract the age correction value for the worker s age at the time of the baseline audiogram from their age at the time of the suspected threshold shift Subtract the difference in the age correction values from the difference between the current and baseline audiograms Take the average of the age corrected threshold shifts at the three required frequencies if the average is greater than or equal to 10 dB an STS has occurred Example 1 A 45 year old male worker has the following audiogram information Test Test Frequency Left Ear Hz Test Frequency Right Ear Hz year m 1000 00 5 000 Baseline 3 4 1990 PPP PE PP eP The data for the left ear show that the threshold shifted by less than 10 dB at all required frequencies Thus an STS could not have occurred in the left ear because the average change at the required frequencies is less than 10 dB Data for 1 000 Hz and 6 000 Hz are not included in the determination of whether an STS has occurred For the right ear a shift of at least 10 dB occurred at each of the r
134. hrough the work area e g maintenance workers are wearing hearing protection iii Supervisors in the area are wearing hearing protection iv Hearing protection is worn correctly v Workers are observed traveling from one noise area to another in the facility l Record the size and shape of the room m Note surface materials on floors walls and ceilings and any acoustical treatment Section III Chapter 5 Page 148 n Take photos of the overall operation machine as well as photos of noise source s and where worker s is in relation to the noise source s o Make an initial determination of potential noise controls If you are recommending engineering controls you need to take tape measurements while in the facility to determine square footage of acoustical controls and to see if barriers booths and other components will fit Cost comparison calculations depend on these measurements 4 End of normal 8 hour shift a Remove dosimeters and record time on OSHA form b Ask worker if this was an average work day for noise exposure normal production day vs sampled day production c Record results of dosimeter sampling on appropriate readout worksheet d If this is an extended shift it is important to document the exposure just before or at the 8 hour mark to provide the 8 hour TWA exposure for comparison against the PEL One can document zero exposure during lunch and subtract that from the sampling time if the
135. idance in interpreting instrument accuracy Other types of sound level meters also exist but do not meet ANSI requirements for the Type 2 or Type designation These meters which are often modestly priced can be useful pre screening tools for employers seeking to identify noisy locations and track improvements during noise reduction efforts They cannot however be used to document compliance with Oregon OSHA standards only properly calibrated Type 2 or Type 1 meters can serve that purpose For example sound level meter applications are available for some smartphones Such an application can give a rough estimate of the noise level in a particular location but may not be used to document compliance with Oregon OSHA standards All sound level meters are affected by temperature and humidity however these instruments are intended to provide reliable readings within the normal range of workplace temperatures During extreme weather temperatures might be considerably outside that range in untempered storage e g the trunk of a parked car Avoid storing noise measurement equipment where the temperature could be lower than 13 F 25 C or higher than 158 F 70 C Avoid carrying cold equipment into a very humid environment which could permit moisture to condense on the instrument To prevent this situation do not keep noise equipment in the trunk of a cold car instead carry it in the passenger compartment and store it indoors at the destinat
136. igure 6 Section III Chapter 5 Page 15 Figure 6 The Fletcher Munson Contours Loudness T a A a o D 2 T gt a a g 5 n n v v c v 500 1 000 Frequency Hz These contours represent the sound pressure level necessary at each frequency to produce the same loudness response in the average listener The nonlinearity of the ear s response is represented by the changing contour shapes as the sound pressure level is increased a phenomenon that is particularly noticeable at low frequencies The lower dashed curve indicates the threshold of hearing and represents the sound pressure level necessary to trigger the sensation of hearing in the average listener Among healthy individuals the actual threshold may vary by as much as 10 decibels in either direction Ultrasound is not listed in Figure 6 because it has a frequency that is too high to be audible to the human ear See Appendix C for more information about ultrasound and its potential health effects and threshold limit values Section III Chapter 5 Page 16 C How We Hear The ear is the organ that makes hearing possible It can be divided into three sections the external or outer ear the middle ear and the inner ear Figure 7 shows the parts of the ear Figure 7 Anatomy of the Human Ear Organs of Balance amp Malleus Semicircular Canals Hammer Incus Anvil Auditory Nerve to the Brain Stapes Stirrup Ear C
137. imize the reduction in noise exposure Of course if a receiver is inside a room reverberations from the ceilings and walls can diminish the effectiveness of a barrier For this reason indoor barriers are most effective when workers are in the direct field of sound from the noise source as opposed to the reverberant field Even outdoors it is possible for noise to reflect from nearby buildings and contribute to the noise exposure of the receiver A noise barrier is most effective when its transmission loss is at least 10 dB greater than the insertion loss expected see text box for definitions of transmission loss and insertion loss If it is not sound transmitted through the barrier may contribute significantly to the noise exposure of the receiver One effective strategy for further reducing noise levels with barriers is to create barriers with multiple layers sandwiching a material of different density such as air between the layers Two 5 inch masonry walls spaced a few inches apart will have a greater transmission loss from one side to the other than a solid masonry wall that is 10 inches thick Section III Chapter 5 Page 88 Insertion Loss vs Transmission Loss Insertion loss is the difference in sound pressure level dB measured at a fixed point before and after the noise control is installed This common measure of acoustic performance represents the change in sound pressure level dB for the surroundings due to the insertion o
138. indblad P R Nyl n E B Svensson E Krieg A Aksentijevic and D Prasher 2006 Audiological Findings in Workers Exposed to Styrene Alone or in Concert With Noise Noise Health 8 45 57 Kishi R I Harabuchi T Ikeda H Yokota and H Miyake 1988 Neurobehavioural Effects and Pharmacokinetics of Toluene in Rats and Their Relevance to Man Br J Ind Med 45 396 408 Lacerda A Lerous T Morata T 2005 Ototoxic effects of carbon monoxide exposure a review Pro Fono Revista de Atualizacao Cientifica Barueri SP v 17 n 3 p 403 412 set dez Lataye R and P Campo 1997 Combined Effects of a Simultaneous Exposure to Noise and Toluene on Hearing Function Neurotoxicol Teratol 19 373 82 Lataye R P Campo and G Loquet 2000 Combined Effects of Noise and Styrene Exposure on Hearing Function in the Rat Hear Res 139 86 96 Lataye R P Campo G Loquet and G Morel 2005 Combined Effects of Noise and Styrene on Hearing Comparison Between Active and Sedentary Rats Noise Health 7 27 49 64 Lataye R K Maguin and P Campo 2007 Increase in Cochlear Microphonic Potential After Toluene Administration Hear Res 230 1 2 34 42 Lawton B W J Hoffmann and G Triebig 2006 The Ototoxicity of Styrene a Review of Occupational Investigations Int Arch Occup Environ Health 79 93 102 Loquet G P Campo and R Lataye 1999 Comparison of Toluene Induced and Styrene Induced Hearing Losses Neur
139. ine which initially generated noise Section III Chapter 5 Page 90 levels of 95 dBA The employer installed acoustical panels around the block machine lowering the noise generated by the machine to 88 dBA The employer stated that the eight acoustical panels cost 45 each for a total cost of 400 Case study A company manufactures mattresses and foundation products The mattresses are assembled on a steel table The nail gun operator who assembles the mattresses was previously exposed to noise levels of 93 dBA The employer implemented the following changes replaced the steel tables with wooden tables reduced the nail gun from 110 psi to 85 psi placed acoustical insulation on the top bottom and around the wooden tables and wrapped foam around the table legs to absorb the vibration to the concrete floor These measures lowered the noise generated to 87 dBA The total cost was 500 ii Damping Case study A high speed strip fed punch press was used in a manufacturing process to stamp electrical components The equipment generated noise levels of 101 dBA when operating at an average of 271 strokes per minute To reduce the noise level the manufacturer installed anti vibration mounts and applied a self adhesive damping sheet to the sheet metal surfaces of the equipment These measures lowered the noise generated by the equipment by 9 dB to 92 dBA Case study A feeder bowl was used to sort aluminum disks and produced 101 dBA The b
140. ing Concepts and Options The rest of this section until the discussion of administrative controls presents information adapted from material developed under contract for the Noise eTool by Dennis Driscoll in 2002 Much industrial noise can be controlled through simple solutions It is important however that all individuals administering abatement projects have a good understanding of the principles of noise control and proper use of acoustical materials Industrial hygienists safety professionals facility engineers and others can make significant progress in reducing equipment noise levels and worker noise exposures by combining their knowledge of acoustics with an understanding of the manufacturing equipment and or processes Reducing excessive equipment noise can be accomplished by treating the source the sound transmission path the receiver or any combination of these options Descriptions of these control measures follow i Source Treatment The best long term solution to noise control is to treat the root cause of the noise problem For source treatment to be effective however a comprehensive noise control survey usually needs to be conducted to clearly identify the source and determine its relative contribution to the area noise level and worker noise exposure At least four methods exist for treating the source modification retrofit substitution and relocation Modification For the most part industrial noise is caused
141. ing noise than others Additionally the way they interrupt noise varies with the frequency of the sound and the physical characteristics of the material The ability of a material to interrupt sound can be described by its ability to absorb sound and separately by the extent to which it does or does not transmit the portion of the sound it absorbs Generally soft thick fuzzy and porous materials absorb sound well permitting only a modest amount of the sound to reflect off the surface back into the space In contrast hard smooth surfaces tend to reflect a high percentage of the sound Heavy dense materials absorb low frequency sounds better than high frequency sounds Protective barriers made of these materials are better at reflecting high frequency sounds but absorb the low frequency sounds A barrier s ability to attenuate sound that it absorbs is described by its transmission loss Transmission loss measured in decibels in laboratory tests represents a sample of a barrier material s ability to prevent sound energy from propagating through the material to produce sound on the other side A sample of material with an excellent transmission loss may reduce the sound level through a test panel of that material by up to 60 dB Both the material and the thickness of the sample influence its transmittal loss When constructing a partial barrier it is important to consider factors other than the barrier material For example for a barrier
142. ion For equipment that must be carried for a brief time into a very cold area to collect a measurement one strategy is to keep the equipment under a coat or otherwise wrapped insulated if possible to keep it from getting cold Sound level meters should be calibrated using the steps outlined in Section 1 above and according to the manufacturer s instructions ii Using a Sound Level Meter Different work environments and different sound level meter microphones might require variations in measurement procedures For practical purposes however certain basic steps apply in most circumstances Section III Chapter 5 Page 50 Figure 17 Sound Level Meter Positioning Confirm that the sound level meter is properly calibrated and temperature stabilized Then position the microphone in the monitored worker s hearing zone Oregon OSHA defines the hearing zone as a 2 foot wide sphere surrounding the head Considerations of practicality and safety will dictate the actual microphone placement at each survey location Note that when noise levels at a worker s two ears are different the higher level must be sampled for compliance determinations Keep in mind that your body or surrounding equipment can influence the noise level acting as a barrier between the noise source and the microphone Hold the sound level meter away from your body to minimize this effect Figure 17 Consult the manufacturer for any specific instructions for positio
143. ion III Chapter 5 Page 104 OSHA 2007 Rules of agency practice and procedure concerning OSHA access to employer medical records Directive Number CPL 02 02 072 Effective Date 8 22 07 OTI Driscoll No date Industrial Noise Online Course 2200 OSHA Training Institute Produced under contract by Dennis Driscoll Quest Technologies 2010 NoisePro Personal Noise Dosimeter User Manual Quest Technologies 2009 QC 10 and QC 20 Sound Calibrators Operator s Manual Quest Technologies 2007 SoundPro Models SE and DL Hand Held Sound Level Meter and Real Time Frequency Analyzer Owner s Manual Seixas N S and Neitzel R 2002 Response to ANPR on Hearing Conservation Program for Construction Workers Occupational Safety and Health Administration Docket H 011G Department of Environmental Health University of Washington October 22 Seixas N and Neitzel R 2004 Noise Exposure and Hearing Protection Use Among Construction Workers in Washington State Department of Environmental and Occupational Health Sciences School of Public Health and Community Medicine University of Washington Seattle September U S Department of Labor 2011 Bureau of Labor Statistics Survey of Occupational Injuries and IlInesses Summary Estimates Charts Package October 11 U S Department of Labor 1983 OSHA Office of Regulatory Affairs Regulatory Impact and Regulatory Flexibility Analysis of the Hearing Conservation Amendment Table 7 Februa
144. ion involves reducing noise at the receiver When deemed practical personnel shelters can be installed or the receiver can be relocated to a relatively quiet area It is important to keep in mind that worker noise exposure is a function of both the magnitude of noise and duration of exposure Therefore receiver treatment works best in areas with high noise for those job activities that are fairly stationary or confined to a relatively small area and where significant time is spent throughout the workday Worker Enclosures Enclosures or personnel shelters can provide a cost effective means for lowering worker noise exposure instead of lowering equipment noise levels Control booths or rooms are commercially available from a number of manufacturers many of which are listed in the Noise and Vibration Control Product Manufacturer Guide see Section VII Resources The cost for these units typically ranges from 5 000 to 35 000 depending on the size and sophistication of their design and their need for electronic controls video monitoring number of observation windows and other features Any of the vendors listed in the manufacturer s guide can provide a cost estimate upon request As a minimum requirement all control rooms should maintain an interior sound level lower than 80 dBA which will minimize worker noise exposure Should there be a need to Section III Chapter 5 Page 42 communicate with workers inside a control room however then a
145. ions and Standards 1 Brief History of Occupational Noise Standards The Occupational Safety and Health Act OSH Act of 1970 built upon earlier attempts in the United States to regulate noise hazards associated with occupational hearing loss In 1969 the Walsh Healey Public Contract Act added the Occupational Noise Exposure Standard as an amendment basing it on the American Conference of Governmental Industrial Hygienists ACGIH noise threshold limit value TLV in effect at that time This set an 8 hour TWA of 90 Section II Chapter 5 Page 28 dBA and a 5 dBA exchange rate for any company with a federal contract worth more than 10 000 This effort to reduce occupational noise hazards was not far reaching but was a first attempt to regulate noise hazards Adopted into the OSH Act in 1970 it served as the basis for OSHA s Noise standard The same 8 hour TWA and exchange rate are still used by OSHA today Also in 1969 the Bureau of Labor Standards promulgated an occupational construction noise standard under the Construction Safety Act which was later adopted by OSHA in 1971 Soon after in 1972 NIOSH published recommendations for an OSHA occupational noise standard which included a recommended 8 hour TWA exposure limit of 85 dBA and a 5 dBA exchange rate However in 1973 OSHA s Standards Advisory Committee maintained the 90 dBA 8 hour TWA with a 5 dBA exchange rate Even though noise energy exposure doubles every 3 dB OSHA thought it im
146. ks from sources such as valves cracked hoses failed seals etc Use programmable logic controllers PLC that integrate all digital sensors along a production line that can shut off the delivery of compressed air when the line or device is off line Should Step 1 3 not be sufficient then retrofit all compressed air devices service and non service type Acoustical Maintenance Section III Chapter 5 Page 171 Acoustical Maintenance 1 To achieve the goal of reducing worker noise exposures sufficiently to eliminate the need for hearing protection or the HCP it will require a combination of noise control measures and then maintaining these controls over time Acoustical Maintenance 2 In addition a critical component in the long term success of the noise control program is to vigilantly keep manufacturing equipment in optimal working condition This will help minimize the noise generated AND it will also minimize the wear and tear on equipment which improves its life expectancy Hence there is a hidden cost savings that can be difficult to quantify but needs to be at least recognized as a benefit Section III Chapter 5 Page 172 Acoustical Maintenance FIGURE 1 6 LINE 1 COMPARISON OF NOISE LEVELS OF CASE LOADER BEFORE amp AFTER ADJUSTMENT Note the heavy impact force upon retracvon of Case OIGE WOS MinIM Zed Mnrough adjusiment by Overa Noise Reducton 90BA maintenance during Me survey
147. ks to Noise eTool on hearing loss is also available in OSHA s eTool Appendices 1 C 1 and 1 C 2 of the eTool provide additional examples of conditions that cause these types of hearing loss Also download the NIOSH Hearing Loss Simulator to understand more about the effects of noise exposure and age on hearing It is important to note that some hearing loss occurs over time as a normal condition of aging Termed presbycusis this gradual sensorineural loss decreases a person s ability to hear high frequencies Presbycusis can make it difficult to diagnose noise related hearing loss in older people because both affect the upper range of an audiogram An 8 000 Hz Notch in an audiogram often indicates that the hearing loss is aged related as opposed to noise induced As humans begin losing their hearing they often first lose the ability to detect quiet sounds in this pitch range E Effects of Excessive Occupational Noise Exposure Workplace noise affects the human body in various ways The most well known is hearing loss but work in a noisy environment also can have other effects 1 Auditory Effects Although noise induced hearing loss is one of the most common occupational illnesses it is often ignored because there are no visible effects It usually develops over a long period of time and except in very rare cases there is no pain What does occur is a progressive loss of communication socialization and responsiveness to the environmen
148. l fresh batteries or recharge reusable batteries with a battery charger All instruments must be calibrated according to the manufacturer s instructions to ensure measurement accuracy 29 CFR 1910 95 d 2 qi All noise measuring instruments used by CSHOs require two types of calibration e Periodic factory level calibration e Pre and post use calibration Both pre and post inspection calibrations are required for any noise instruments used by CSHOs It is important to understand the difference between these two types of calibrations Calibrators must also be calibrated on an annual basis Equipment manufacturers typically recommend periodic calibration on an annual basis These rigorous testing protocols ensure that the electronic components are in good working order and detect shifts in performance that indicate gradual deterioration Periodic calibration results in a calibration certificate documenting the standard of performance Typically the instrument will also receive a sticker indicating its last calibration date and when the next periodic calibration is due An instrument owned by Oregon OSHA that is past its calibration due date must be returned to the Oregon OSHA Laboratory to have its calibration renewed Do not continue to use it past the calibration date Section III Chapter 5 Page 46 The Oregon OSHA Laboratory is qualified to perform periodic calibration for the noise monitoring instruments commonly issued to C
149. l to be noticeable by touch Large flat surfaces that vibrate are likely to radiate more noise than smaller stiffer surfaces It is often not cost effective especially for large machines to treat the entire machine with damping materials Damping material attached to the center of a vibrating plate is more effective than the same amount of material attached on the sides of the same plate This concept is displayed in Figure 33 in which a circular blade is outfitted with a sheet metal disc with a rubber buffer layer between the sheet metal and the blade Figure 33 Adding Damping Material to a Saw Blade rubber sheet metal as large diameter as possibile reinforcements Section II Chapter 5 Page 77 Reducing Structure Borne Noise by Vibration Isolation When a machine rotates cycles and indexes it often transfers some vibratory energy in the casing pipes and metal structure Even though these parts of the machine may not be an efficient radiator of airborne sound the vibrations can be carried via solid connections to a surface area that can convert this energy into airborne sound or noise When structure borne vibration is identified as a primary source isolation of the exiting force from the structure is the most desirable and effective control Figure 34 represents a vibrating piece of equipment that has been isolated using spring isolators to prevent noise transfer into the concrete floor Driscoll Principle
150. le place the microphone on the side of the worker closest to the primary noise source if there is one c Once the dosimeter is in place ask the worker if it feels all right confirm that the cord is not in the way of their work and emphasize that the worker should continue to work in a routine manner Always document the type of hearing protection worn by the worker When the type and model of personal protective equipment is not recorded on the sampling sheet it is difficult to confirm that the hearing protection s NRR is adequate to protect the worker from the measured d Tell the worker that you will check back regularly and to let you know right away if there is a problem with the unit or with wearing it Instruct the worker being sampled not to remove the dosimeter unless absolutely necessary and not to cover the microphone with a coat or outer garment or move the microphone from its installed position Let the worker know when the dosimeter will be removed For example explain to the worker that you will be collecting the noise dosimeters prior to lunch and then after lunch you will resume sampling them i If workers eat in their work area and lunch is part of the 8 hour workshift you might consider leaving the dosimeter on during lunch Section III Chapter 5 Page 146 e Record necessary information about the worker e g job title name of department job description type of hearing protection worn length of em
151. lity a If so document type of hearing protection provided to workers 4 Question union representative on noise and hearing conservation efforts Section III Chapter 5 Page 142 H 3 Walkaround 1 CSHO will conduct noise screening to determine whether dosimetry is necessary Remember to lead by example Conscientiously wear your hearing protection and other appropriate personal protective equipment consistently and correctly during your inspection Building rapport is important Use a conversational tone and take an interest in what is going on This approach will foster a practical dialog and helpful information exchange a Record noise levels on schematic diagram or draw your own floor plan of area s where screening was conducted b Document sources of noise e g machines processes c Take SLM measurements in worker s hearing zone 2 foot diameter sphere around head and document those results d Take photos of workers with improperly worn earplugs and workers in noisy areas without hearing protection interview these workers later 2 CSHO will interview workers in elevated noise areas gt 80 dBA CSHOs shouldn t feel that they are limited to scripted questions but should be flexible to pursue relevant leads and unanticipated responses It may be helpful to comment on observations particularly at the time and in the area of the observation e g I see some people wearing earplugs and others not using a
152. loss can be found in 29 CFR1904 10 The effects of excessive noise exposure are made worse when workers have extended shifts longer than 8 hours With extended shifts the duration of the noise exposure is longer and the amount of time between shifts is shorter This means that the ears have less time to recover between noisy shifts As a result short term effects such as temporary threshold shifts can become permanent more quickly than would occur with standard 8 hour workdays Tinnitus or ringing in the ears can occur after long term exposure to high sound levels or sometimes from short term exposure to very high sound levels such as gunshots Many other physical and physiological conditions also cause tinnitus Regardless of the cause this condition is actually a disturbance produced by the inner ear and interpreted by the brain as sound Individuals with tinnitus describe it as a hum buzz roar ring or whistle which can be short term or permanent Acoustic trauma refers to a temporary or permanent hearing loss due to a sudden intense acoustic or noise event such as an explosion 2 Worker Illness and Injury Reports The U S Bureau of Labor Statistics BLS publishes annual statistics for occupational injuries including hearing loss reported by employers as part of required recordkeeping The BLS data show that hearing loss represented 12 of the occupational illnesses reported in 2010 Figure 9 This represents more than 18
153. loud equipment The agency determined that a two prong approach was needed buying new quiet equipment while continuing to retrofit old noisy equipment By implementing a Buy Quiet and Quiet by Design requirement the agency compelled noise emissions to be considered equally with other factors when buying equipment Section III Chapter 5 Page 91 near an 80 dBA threshold Among other tools in a Buy Quiet Process Roadmap created to help procurement officers identify and purchase quieter equipment the agency developed a process for quantifying the long term costs of noise exposure for the candidate products being considered for purchase Both these costs and the equipment noise level are considered in the final purchase decision Case study A standard pneumatic production rock drill was compared to a prototype pneumatic rock drill incorporating engineering noise control measures varying thrust pressure and water flow rate at the bit By using the manufacturer s recommended operating pressure of 496 kPa 72 psi the prototype s sound power was 10 dBA less than that of the standard drill The drills penetration rates were within 6 percent of each other indicating that the noise control was effective without sacrificing performance NIOSH 2009 iv Isolation Case study A bench grinder and finish grinder in an electrical contractor s workshop were resting on a metal cabinet against the wall The equipment generated noise levels of 95 dB
154. lts If a worker exhibited a temporary threshold shift consider whether facility managers took appropriate action Check the OSHA 300 Logs to determine whether the employer has reported cases of hearing loss The employer should be asked how the determination was made to re establish baselines and about any apparent hearing loss cases recorded or those cases not recorded on the OSHA 300 Logs Compare the most recent audiogram with the baseline audiogram If a Standard Threshold Shift STS is observed review data for intervening years to determine when the STS occurred The baseline audiogram is usually but not always the first audiogram If a later audiogram shows lower hearing thresholds that would be the baseline If a persistent STS is identified the following audiogram would be adopted as the revised baseline for future comparisons Evaluate data for each ear separately A threshold shift can occur in one ear and not the other Use threshold data only for the three required frequencies 2 000 3 000 and 4 000 Hz Compare each audiogram to the baseline and take the average of the difference in the threshold at the three Section III Chapter 5 Page 65 required frequencies If the average is less than 10 dB no STS has occurred If the average is 10 dB or more the age correction values must be applied to determine whether an STS has occurred To apply the age correction values subtract the age correction value for the worker s age
155. machine feeders e SIC 26 paper and paper industry paper goods machine operators e SIC 28 through 30 printing and publishing chemicals and petroleum and plastics and rubber industries chemical equipment operators SIC 28 and 29 laborers and freight movers SIC 28 and 29 grinding machine operators SIC 30 and helpers SIC 30 e SIC 32 nonmetallic minerals industry inspectors testers and sorters extruding forming and pressing machine operators hoist and winch operators unspecified operators e SIC 33 and 34 primary metal and fabricated metal products industries forging machine operators grinding and lapping machine operators and welders e SIC 35 through 39 various equipment manufacturers milling and planing machine operators coil winders and tapers forging machine operators grinding and lapping machine operators and abrasive blasters Section III Chapter 5 Page 26 3 Summary of Construction Industry Noise Exposure by Trade and Activity Table Il 6 Summary of Average TWA Construction Noise Exposure from University of Washington Noise Monitoring Research Trades Monitored Source Adapted from Seixas and Neitzel 2002 Submittal to OSHA s Advance Notice of Proposed Rulemaking Docket H 011G Table Il 7 Task Specific Average Noise Levels by Construction Trade TRADE gt eas ee Average dBA for Tasks Event Each Task Event CARPENTER Shop work oss Stripping forms Interior finish os
156. matic is a useful strategy for recording noise levels in context The diagram can help determine which workers have noise exposure and it is useful for communicating with workers and the employer Use a plant schematic or sketch the general floor plan Mark and identify noisy processes Use the sound level meter to determine the noise level adjacent to the noisy equipment or process and at various distances from the noise source Specifically measure noise at the ear position of workers in the vicinity Next move away from the noise source making sequential measurements to determine the hazard radius the distances from the noise source at which the noise level drops to the PEL and below the AL Figure 25 Mark the distances in the sketch Also the dimensions of the work area and the materials that were used to construct the room should be identified Section III Chapter 5 Page 68 Figure 25 Taking Measurements for a Noise Diagram Your completed sketch will show a series of contours around the noise source s Figure 26 Expect the contours for adjacent noise sources to overlap Workers operating entirely outside the contour are not exposed to noise in excess of the AL Workers whose tasks take them closer to the equipment might experience exposures between the AL and the PEL or even in excess of the PEL Take photographs to document the type of equipment or process Figure 26 Drawing a Noise Diagram Where noise l
157. meter to document the noise levels For each noise level include a description of the noise source including a photograph record the distance from the source at which the measurement was made and note how many and which workers are potentially exposed Also note that if a noise is intermittent the frequency and duration of the noise as well as both A and C weighted noise levels must be identified unless octave band analyzer readings are possible Interview workers and supervisors to inquire about which areas they think are most noisy at the site Also ask which are the noisiest areas in which they work As you visit these areas identify the sources of noise and use the noise sound level meter to determine whether sound levels could be hazardous Select workers for noise dosimetry and carefully explain the process including the fact that the microphone only measures how loud or quiet the noise is it does not record speech Follow the dosimeter manufacturer s instructions to set up and use the instrument being careful to record the time the instrument is turned on and off Throughout the day use the sound level meter to corroborate the noise dosimeter readings Readings taken at times when significant noise events occur can be particularly useful as are series of sound level readings obtained at regular intervals e g once or twice per hour or 10 times per shift 1 Create a Noise Diagram Noise Mapping The noise diagram or sche
158. n Hexane Carbon disulfide The rat cochlea is sensitive to aromatic solvents unlike that of the guinea pig or chinchilla Campo et al 1993 Cappaert et al 2003 Davis et al 2002 Fechter 1993 These findings have been attributed to metabolic and other toxicokinetic differences Campo and Maguin 2006 Davis et al 2002 Gagnaire et al 2007 Because of their metabolism rats are considered comparatively good animal models for the investigation of the ototoxic properties of aromatic solvents in humans Campo and Maguin 2006 Kishi et al 1988 Examples of relevant literature on interactions between noise and specific substances include Toluene Brandt Lassen et al 2000 Johnson et al 1988 Lataye and Campo 1997 Lund and Kristiansen 2008 Styrene Lataye et al 2000 Lataye et al 2005 M kitie et al 2003 Ethylbenzene Cappaert et al 2001 Trichloroethylene Muijser et al 2000 Carbon monoxide Lacerda et al 2005 Lead CDC HHE 2011 Section III Chapter 5 Page 127 Lataye et al 2005 found interactive effects of noise at 85 dB with a styrene exposure concentration of 400 parts per million ppm In general though high levels of noise and high concentrations of solvents were used in most of these investigations Because of these special conditions extrapolation to occupational exposure conditions can be challenging Cary et al 1997 Investigators suggest that exposure to these solvents can pr
159. n iei e eE G ae m E a a E A 17 E Effects of Excessive Occupational Noise Exposure 19 1 Auditory Effects 2 222 cceeeneeiSecsedesadeenes sGedand 20 2 Worker Illness and Injury Reports 04 20 3 Ofer Effets soy o55 5 40884 a bse G ESS sao S ee eee oh 21 Fs UltfasONiC enea n n E E E E A 22 G Noise and Solvent Interactions snuuuunuua unuraa 22 H Affected Industries and Workers 2 0 2 eee eeeee 23 1 Affected Industries 2 4dcesnccadesuderiSerencesaues 23 2 Historically Affected Jobs in General Industry 26 3 Summary of Construction Industry Noise Exposure by Trade and ACV LY eeren er e ooh eS ce Oe PSK RES e a er ROE KS 27 Section III Chapter 5 Page 3 TABLE OF CONTENTS CONTINUED I Regulations and Standards 0 0 0 ee eee eee eee 28 1 Brief History of Occupational Noise Standards 28 2 Oregon OSHA Noise Standards 00000 29 J Noise Exposure Controls Overview 0000 eee eee 31 1 Hierarchy of Controls for Noise 0 00000 00 8 31 2 Noise Control Engineering Concepts and Options 32 3 Administrative Controls 0 0 eee eee eee 43 4 Personal Protective Equipment Hearing Protection 44 IIL MEASUREMENTS 325645559 4G 0608500455945 SEG eVEo EW ee 46 A BQWIPIMGM 2 rcescbctdecasdssdeeusersdenetesstoesneesges 46 1 Noise Evaluation Instrument Care and Calibration
160. n program was determined to be Section III Chapter 5 Page 140 1 300 per year or 38 000 for 30 years This value is incorporated into NASA s cost benefit calculations for noise control projects G 3 References Berger et al 2003 Hearing Loss Statutes in the United States and Canada Chapter 18 Table 18 1 in The Noise Manual 5th Edition American Industrial Hygiene Association pp 692 696 Bowes et al 2006 Long Term Cost Benefit of Noise Control on Ships Document Number CRM D0014732 A2 Final CNA Corporation Colgate Palmolive 2012 Presentation Safe In Sound Excellence Award Driscoll D P 2010 Presentation The Economics of Noise Control Engineering Versus the Hearing Conservation Program Professional Conference on Industrial Hygiene PCIH American Board of Industrial Hygiene Driscoll D P 2012 Personal communication with D Driscoll and ERG March 28 Driscoll D P and L H Royster 2003 Benefits and Costs of Noise Control In Berger et al eds The Noise Manual 5th Edition American Industrial Hygiene Association pp 281 9 National Aeronautics and Space Administration Buy Quiet Process Roadmap Nelson D A 2012 The Long Term Cost of Noise Exposure NIOSH 2012 NIOSH Update NIOSH and NHCA present 2012 Safe In Sound Excellence in Hearing Loss Prevention Awards NIOSH Web page February 23 Section III Chapter 5 Page 141 APPENDIX H Job Aid Steps and Checklists for Conducti
161. n the Insp column represents the number of inspections in which one or more citations were issued Note that the total is not the sum of the number of inspections associated with each standard cited multiple standards may be cited in one inspection Interpreting the table Citations were issued during nine inspections conducted in SIC 2047 between October 2010 and September 2011 FY 201 D OSHA s noise standard 1910 95 was cited during two 22 of those nine inspections see column Insp Overall the noise standard was cited twice putting it among the 10 most frequently cited standards in this industry for that year The dollar penalties for noise standard violations accounted for 2 of the total 74 774 in penalties associated with citations issued in SIC 2047 in FY 2011 Section II Chapter 5 Page 63 Few inspections likely occurred in a small industry during a single year For this reason for smaller industries the CSHO might obtain additional useful information by searching a wider range of dates e g several years Select Search Inspections By SIC and enter the SIC or NAICS and the date range desired The resulting data table shows all the inspections conducted in that industry within the requested time period The table indicates the number of violations for each inspection but does not list them individually Clicking on the inspection number however will open the inspection s information screen showing which standards were
162. n the perception of having the higher level of power to which they are accustomed which is based on their subjective assessment of the sound level To prevent unnecessary or unauthorized air adjustments by the process or equipment operators air pressure regulators should be set and locked to ensure that they cannot be modified without a supervisor s consent and operators should be educated and trained in determining whether the power is adequate Substitute for the Source Another source treatment involves using alternative equipment or materials that are inherently quieter yet still meet the production needs This option is called substitution for the source Often equipment manufacturers have alternative devices that perform the same function at lower noise levels These quieter devices typically cost more however as they require tighter tolerances and more precision as they are manufactured Therefore when applicable it will be necessary for the user to determine if the noise reduction benefit justifies the additional cost The supplier s or the manufacturer s website should be consulted to learn if quieter equipment is available and at what additional cost Examples where alternative and quieter equipment may exist include e Gears e Bearings e Fans or blowers Section III Chapter 5 Page 38 e Control valves e Air compressors e Conveyors e Electric motors e Pumps There might also be opportunities to replace equipment with
163. nal study Schaper et al 2003 Schaper et al 2008 on the relationship between hearing impairment measured by pure tone audiometry and occupational exposure to toluene and noise has not found ototoxic effects in workers exposed to a concentration of toluene lower than 50 ppm The observed hearing loss was associated only with noise intensity Section III Chapter 5 Page 128 However the use of hearing protection was not taken into account in the conclusions relative to the potential interaction between noise and toluene on hearing A clear relationship between solvent and hearing impairment is difficult to assess through the available epidemiological studies The workplace environments where noise and solvents can be simultaneously present are typically complex for example see critical review of Lawton et al 2006 Hoet and Lison 2008 Quite often the workers were exposed to multiple substances Furthermore most of these studies had a cross sectional design that featured a number of weaknesses in the interpretation of the findings For instance chronic effects were related to currently measured exposures In some cases the exposure concentrations measured at the time of the study were markedly lower than those ascertained in past years Morata et al 1993 All in all there are limited data on dose response relationships or clear effects on auditory thresholds in humans for reviews see Lawton et al 2006 Hoet and Lison 2008 How
164. nance panels and equipment controls provide ventilation or keep the process flowing In these cases a partial enclosure may still substantially reduce noise Like full enclosures partial enclosures should have effective barrier materials on the outside and should be lined with Section HI Chapter 5 Page 86 absorptive materials on the inside Because noise will escape through the opening the noise path should be treated with sound absorbing materials if possible Also the number of openings should be limited and should be directed away from workers if possible Figure 40 shows a partial enclosure that allows access while affording the operator some protection from the noise source Where possible it is beneficial to combine noise control with machine guarding requirements to protect workers from other physical hazards e g pinch points crushing hazards For more information on integrating noise control with machine guarding see Appendix K Three Ways to Jump Start a Noise Control Program Figure 40 Partial Enclosure tah haa i vg Pn va Runata 0 POO TOO e ee eee yn te hs Fens CENA fh PAN al t ing ir En i materials a on the inside Driscoll Principles of Noise Control Enclosing a noise source is often impractical if there is not enough space or if workers need to access the noise source for maintenance or operational reasons In these cases lagging could be a more practi
165. nce examples of controls have been determined write a citation for 29 CFR 1910 95 b 1 In addition cite for any deficiencies in the employer s hearing conservation program 4 Another scenario may involve 8 hour TWA exposures between 85 dBA and 90 dBA 80 dBA threshold The employer has an existing hearing conservation program The CSHO shall review the existing program and cite for any deficiencies in the program Cite 1910 95 c 1 and deficient elements of the program 5 Another scenario could involve 8 hour TWA exposures between 85 dBA and 90 dBA 80 dBA threshold but the employer has no existing hearing conservation program The CSHO shall cite 1910 95 c 1 only H 6 Closing Conference 1 Discuss apparent violations 2 Provide copy of sample results 3 Discuss abatement e g review engineering controls that you are recommending 4 Discuss possible citations 5 Discuss informal conference 6 Discuss contesting 7 Discuss posting requirements The specific penalties should not be discussed just the possibility that there may be penalties assessed as a result of the inspection H 7 Follow up Inspection Once abatement has been completed the CSHO will conduct a follow up inspection to verify the effectiveness of the engineering controls Section III Chapter 5 Page 151 H 8 Example questions to ask employer about hearing conservation and noise e What are your loudest areas of the facility and the loude
166. nd power levels Total L 10 logro 1048 10 Section II Chapter 5 Page 118 Often using this equation to quickly sum sound levels when there is no calculator or computer available is difficult The following table can be used to estimate a sum of various sound levels Difference Between Two Levels Amount to Add to Higher Level to to Be Added Find the Sum Example There are three noise sources immediately adjacent to one another each producing a sound level of 95 dB The combined sound level can be found using the table above The difference between the first two noise sources is 0 dB which means the sum will be 95 3 98 dB The difference between 98 dB and the remaining noise source 95 dB is 3 which means the sum will be 98 2 100 dB B 4 Adding Noise Exposure Durations to Determine Compliance with OSHA Standards Under OSHA standards workers are not permitted to be exposed to an 8 hour TWA equal to or greater than 90 dBA OSHA uses a 5 dBA exchange rate meaning the noise level doubles with each additional 5 dBA The following chart shows how long workers are permitted to be exposed to specific noise levels Permissible Duration Sound Level Hours per Day dBA Slow Response The values in the chart above are from Table G 16 in the general industry standard 29 CFR 1910 95 To calculate a permissible duration that is not addressed in this chart use the following equation ja 2 L 90 5 Section III
167. ne diffuser silencers and expansion chamber silencers These function by providing the escaping exhaust air stream a larger area through which to expand and exit so the air is released at a lower speed and pressure This control option can cut noise by 20 dB or more e Purchasing equipment that comes with these features and replacing the noise control nozzle or silencer if function deteriorates e Adjusting the angle of air jets so that lower air pressure is needed to move products In some cases a more precise nozzle will permit further reductions e Updating workplace policies to reduce reliance on compressed air where it is unnecessary For example vacuuming instead of using compressed air for cleaning This method also reduces air contaminants such as spilled or settled dust containing a hazardous substance that would become airborne when blown with compressed air For more information on controlling noise from pneumatic and compressed air systems see Appendix K Three Ways to Jump Start a Noise Control Program Section III Chapter 5 Page 74 Figure 30 Noise Reducing Compressed Air Nozzles v Retrofit Applications Reduce Response of Vibrating Surfaces by Vibration Damping Damping is another means of noise reduction It dissipates energy associated with vibration often using a coating applied to the surfaces of the noise source For example in parts manufacturing metal parts are transferred via metal chutes causing
168. network chart for each value Lp T_ corrected to the A scale Li The A weighted sound level is calculated by combining the corrected band levels Ls 10 x logis 7104 2 10 x log 1055 105 1075 10 10 10 10 93 1094 107 105 Where La is the A weighted sound level and Li is the corrected decibel level value for each individual octave band Section III Chapter 5 Page 121 B 6 Calculating Sound Pressure Level at a Distance If a sound is generated at a point source in a free field meaning there are no walls or other obstructions the sound pressure level Lp will be reduced by 6 dB each time the distance from the noise source is doubled Alternatively L will increase by 6 dB in a free field each time the distance to the noise source is halved Consider the following example ac Generator Surveyor Example A worker is surveying an open field which has a diesel generator running in the middle of it The worker is 100 ft from the generator and is exposed to a noise level of 85 dBA When the worker is 25 ft from the generator the noise level will be 97 dBA At 200 ft from the generator the worker will be exposed to a noise level of 79 dBA Calculating the sound pressure level at a specific distance from a noise source is often useful The following equation allows one to calculate the sound pressure level at any distance from a noise source in a free field Lpa2 Lpa 20 x log
169. ng a Noise Inspection H 1 Pre Inspection Activities 1 CSHO receives an assignment with potential exposures to noise 2 CSHO prepares for inspection a Calibrates noise equipment and documents calibration for sound level meter SLM noise dosimeters and octave band analyzer OBA b Brings necessary OSHA forms to record measurements 3 CSHO researches previous history on company e g previous noise citations H 2 Opening Conference Note Attempt to open early in the day as close to the commencement of the workday as possible this will not always be possible Especially if the inspection is a complaint hold an abbreviated opening and then proceed directly to the complaint or referral area to deploy dosimeters take initial SLM readings and conduct a rough sketch of the area 1 Explain purpose nature and scope of inspection 2 CSHO requests the following records information for review if available a 300 Logs Check for recordable hearing losses in the Hearing Loss Column M 5 b Audiograms for the previous 3 years i Determine if any worker should be recorded on 300 Logs both situations must exist in same ear STS and 25 dB above audiometric zero c Employer noise sampling data d Departments areas where noise may be an issue e Training records for hearing conservation program f Schematic diagram of facility for noise mapping 3 Ask if hearing protection is required or voluntary anywhere in the faci
170. ng an engineering control administrative control or a form of personal protective equipment to reduce the noise level if noise exposure is too high Driscoll Principles of Noise Control 1 Hierarchy of Controls for Noise The hierarchy of controls for noise can be summarized as 1 prevent or contain the escape of the hazardous workplace agent at its source engineering controls 2 control exposure by changing work schedules to reduce the amount of time any one worker spends in the hazard area administrative controls and 3 control the exposure with barriers between the worker and the hazard personal protective equipment This hierarchy highlights the principle that the best prevention strategy is to eliminate exposure to hazards that can lead to hearing loss Corporations that have started buy quiet programs are moving toward workplaces where no harmful noise will exist Many companies are automating equipment or setting up procedures that can be managed by workers from a quiet control room free from harmful noise When it is not possible to eliminate the noise hazard or relocate the worker to a safe area the worker must be protected with personal protective equipment Note See Chapter 2 Section XIII of the Oregon OSHA FIRM Compliance Officer s Guide for current citation policy when addressing engineering administrative controls versus hearing conservation program Section III Chapter 5 Page 31 2 Noise Control Engineer
171. ng and administrative controls are essential to an effective hearing loss prevention program They are technologically feasible for most noise sources but their economic feasibility must be determined on an individual basis In some instances the application of a relatively simple noise control solution reduces the hazard to the extent that the other elements of the program such as audiometric testing and the use of hearing protection devices are no longer necessary In other cases the noise reduction process may be more complex and must be accomplished in stages over a period of time Even so with each reduction of a few decibels the risk of hearing loss is reduced communication is improved and noise related annoyance is reduced The first step in noise control is to identify the noise sources and their relative importance This can be difficult in an industrial setting with many noise sources It can be accomplished through several methods used together obtain a frequency spectrum from an octave band analyzer turn various components in the factory on and off or use temporary mufflers or enclosures to isolate noise sources and probe areas close to equipment with a sound level meter to pinpoint areas where sound is dominant These measures will aid in identifying the sound sources that affect workers the most and should be prioritized when implementing noise controls Once the noise sources have been identified it is possible to proceed in choosi
172. ning the model of sound level meter you plan to use This may be particularly important when measuring in unusual settings For example the manufacturer may have specific instructions for sound level readings in a non reverberant environment Use a wind screen to reduce measurement errors caused by wind turbulence over the microphone Typical wind screens are made of soft foam rubber and are designed to fit over the microphone Figure 18 Although not necessarily needed indoors if air movement is minimal a wind screen can be left in place for all measurements Collected measurements can be affected by anything that comes across the face of the sound level meter microphone such as hair shirt collars scarves or other objects The use of a wind screen reduces the effects of this incidental contact Wind screens have the added advantage of protecting the microphone at least somewhat from damage resulting from impact dust paint overspray and moisture Section II Chapter 5 Page 51 Figure 18 Wind Screen Most Type 1 and Type 2 sound level meters can be set to respond with either a slow response or a fast response The meter dynamics are such that the meter will reach 63 of the final steady state reading within one time constant Fast response corresponds to a 125 millisecond ms time constant Slow response corresponds to a second time constant The meter screen shows the average sound pressure level measured by the mete
173. nt for low frequency and high frequency noise As a general guideline low frequency noise is more difficult to control Certain instruments that measure sound level can determine the frequency distribution of a sound by passing that sound successively through several different electronic filters that separate the sound into nine octaves on a frequency scale Two of the most common reasons for filtering a sound include 1 determining its most prevalent frequencies or octaves to help engineers better know how to control the sound and 2 adjusting the sound level reading using one of several available weighting methods These weighting methods e g the A weighted network or scale are intended to indicate perceived loudness and provide a rating of industrial noise that indicates the impact that particular noise has on human hearing The following paragraphs provide more detailed information 9 Octave Bands Frequency Bands Octave bands a type of frequency band are a convenient way to measure and describe the various frequencies that are part of a sound A frequency band is said to be an octave in width when its upper band edge frequency fz is twice the lower band edge frequency fy f2 2 fi Each octave band is named for its center frequency geometric mean calculated as follows fe fif2 where f center frequency and f and f are the lower and upper frequency band limits respectively The center lower and upper frequencies for
174. nything Why is that a Examples of questions to ask workers related to noise 1 2 In your opinion is today a typical noise exposure day In your opinion what are the loudest jobs at work So tell me when you first started working here or when they first gave you hearing protection what happened Did you get a choice as to what type What types are available Did anyone explain why you have hearing protection and where and when you need to use it How did they do that Section II Chapter 5 Page 143 6 Depending on the type of hearing protection used the questioning might go different ways e g disposable muffs reusable plugs 7 Are you supposed to wear hearing protection If so how often Note If worker answers no ask why he she doesn t wear it 8 Are there certain jobs or areas where you must wear hearing protection 9 In what areas in the facility are you required to wear hearing protection CSHOs should try TO DO DOSIMETRY THE DAY OF THE OPENING Sometimes a return trip is necessary but as a general rule one should be able to start sampling ASAP It takes very little time to deploy the dosimeters and significant data are lost by not seizing the opportunity You typically can get 6 hours in these situations which often is sufficient to support a citation Another option is to open later in the day and do a full shift sample in the evening Second shift is a great time to sample as
175. of the ratio of the instantaneous pressure fluctuations above and below atmospheric pressure to the reference pressure Lp 10 x logio P Pret Where P is the instantaneous sound pressure in units Pa and Pye is the reference pressure level defined as the quietest noise a healthy young person can hear 20 uPa Example If a piece of equipment has a sound pressure of 2 Pa the sound pressure level is calculated Lp 20 logio 2 0 00002 20 logio 100 000 20 x 5 0 100 dB B 2 Sound Power Level Sound power level Lw is similar in concept to the wattage of a light bulb In fact Lw is measured in watts W Unlike Lp Ly does not depend on the distance from the noise source The sound power level is calculated using the following equation Ly 10 x logio W Wee Where W is the acoustic power in watts and Wer is the reference acoustic power 10 Example The sound power level associated with a typical face to face conversation which may have a sound power of 0 00001 W is calculated Lw 10 x log1o 0 00001 10 70 dB B 3 Combining and Averaging Sound Levels Decibels are measured using a logarithmic scale which means decibels cannot be added arithmetically For example if two noise sources are each producing 90 dB right next to each other the combined noise sound level will be 93 dB as opposed to 180 dB The following equation should be used to calculate the sum of sound pressure levels sound intensity levels or sou
176. oise dose of all the bulldozers 139 OSHA PEL The operator of the new bulldozer with intact noise controls except cab had noise exposures 1 4 to 1 10 that of workers operating dozers lacking noise controls but otherwise in good condition up to 1 397 OSHA PEL NIOSH 1979 Section III Chapter 5 Page 92 vii Silencing Pneumatic Case study A manufacturing process involved the use of a hoist motor for materials handling The motor s air exhaust exposed the operator to 115 dBA The manufacturer installed a muffler on the exhaust reducing the noise level to 81 dBA Off the shelf mufflers cost anywhere from 1 to 150 each plus the cost of maintenance labor which can be assumed to be 27 per hour in 2009 dollars for 1 hour per month Case study A powder mill dropped ground product by gravity into a large orbital sifter This process generated a noise hazard for the equipment operators but the powder would destroy a traditional silencer The facility manufactured a flexible connector between the pipe and the sifter that allowed the sifter to move and stay connected to the pipe above while not allowing the sifter to direct noise energy through the inlet An oversized silencer was then fitted over the flexible connector to catch the noise that leaked from the connector reducing the noise level by 8 dB to 82 dB The cost was 750 equivalent to 1 309 34 at the time 2005 Case study A pneumatic nail gun generated a noise level of
177. oise level than the level that would have existed in the absence of any reflecting surfaces A user must understand and apply the principles of room acoustics when adding sound absorbing materials to the walls and ceiling to reduce the noise levels throughout the room If a user installs sound absorption in a room without putting any science behind the decision then the likelihood of success will be tenuous at best Using sound absorption on a room s surfaces has both advantages and disadvantages Advantages e Provides a significant reduction in the reverberant sound buildup especially in pre existing hard surface spaces e Works best in relatively small volume rooms or spaces lt 10 000 ft e Requires minimal maintenance after initial installation e Can be purchased and installed at a reasonable cost e Works best on middle to high frequency noise Disadvantages e Room treatment does nothing to address the root cause of the noise problem e Does not reduce noise resulting from direct sound propagation e The absorption can deteriorate over several years and may need periodic replacement perhaps every 7 to 10 years e Rarely does this form of treatment eliminate the need for hearing protection Keep in mind that adding sound absorption to decrease the reflected or reverberant noise in a room will do nothing to reduce the acoustical energy propagating by direct line of sight from the source Therefore it is helpful for the
178. ollow up monitoring will focus on noise dosimetry prepare to arrive in time to start monitoring with calibrated equipment just as the shift begins The goal is to sample for a full 8 hours or 8 hours plus the lunch break period if the break is not included in the dosimetry See Appendix H for extensive information on conducting noise inspections The appendix addresses by section e Pre inspection activities e The opening conference including a list of documents to request e Suggestions for the walkaround portion of the investigation including sample questions for workers e Advice on using noise dosimeters to collect full shift samples when the workday is not exactly 8 hours long e Considerations for post inspection activities including a list of items to discuss at the closing conference e Follow up inspections e A list of example questions to ask the employer about hearing conservation and noise V Hazard Abatement and Control A Engineering Controls Engineering controls meant to reduce noise levels can take many forms They can reduce noise at the source by replacing or modifying equipment or they can reflect or absorb noise along the transmission path before it reaches the receiver HPDs worn by a worker also block noise before it reaches the receiver s i e the worker s ears but because they are worn by the worker HPDs are considered personal protective equipment rather than engineering controls For hearing lo
179. ols published by OSHA Region III This appendix reviews four alternatives for evaluating the benefits and costs of noise control e American Industrial Hygiene Association AIHA Benefits and Costs of Noise Control In The Noise Manual AIHA 2003 or latest edition in the 2003 edition see Chapter 9 Noise Control Engineering e Additional detail Driscoll The Economics of Noise Control Engineering Versus the Hearing Conservation Program e Example Colgate Palmolive winner 2012 Safe in Sound award e National Aeronautics and Space Administration NASA Buy Quiet Roadmap G 1 AIHA Benefits and Costs of Noise Control In The Noise Manual Chapter 9 AIHA outlines a procedure for comparing the benefits and costs of noise control Driscoll and Royster 2003 Section III Chapter 5 Page 136 G 1 1 The Noise Manual The AIHA chapter recognizes that employers wonder What magnitude of noise reduction in the employees TWA is possible and is it worth doing That is if an employee s TWA can be reduced by 3 dBA using noise control should it be achieved The chapter encourages the reader to consider the potential magnitude of noise reduction and then prioritize efforts using a series of steps The first step is identifying realistic short and long term goals A short term goal could be to reduce the noise exposure of the most highly exposed workers to a level that makes it easier to protect them e g with administrative contr
180. ols or personal protective equipment A long term goal could be to reduce all noise exposure to nonhazardous levels which can result in cost savings by eliminating the need for hearing conservation programs and additional worker compensation expenses To set priorities AIHA suggests that important considerations include e The number of workers affected by the noise source or sources e The potential for the noise to significantly damage their hearing e The characteristics of the noise which can affect the control options Is it a pure tone Impulse noise e How likely it is that the intervention will succeed in meeting the organization s goals e Whether the control method will increase decrease or have a neutral effect on productivity e The estimated cost of the control including purchase installation and maintenance Promoting a systematic evaluation AIHA offers various factors that an employer can assign to these considerations and then process using an equation that divides the product of these factors by the estimated cost G 1 2 Additional Detail Driscoll The Economics of Noise Control Engineering Versus the Hearing Conservation Program One of the authors of The Noise Manual AIHA 2003 or latest edition chapter Dennis Driscoll has outlined a method for determining the cost of a hearing conservation program in more detail This method considers 18 costs in the annual hearing conservation program cost Section
181. ons under OSHA s noise standards To access inspection records start at OSHA s website home page and choose the Data amp Statistics tab near the top of the page Select Frequently Cited OSHA Standards from Section III Chapter 5 Page 62 the options presented and enter the SIC or NAICS Figure 24 When the search page opens enter the SIC of the industry of interest and click Submit If the SIC is not available use the SIC lookup link on that page to select an appropriate code The search provides a table of results a ranked list of the standards cited in that industry for the previous fiscal year Using SIC 2047 Dog and Cat Food Manufacturing as an example again the search showed that 1910 95 was the 10th most frequently cited standard in this industry that year The search returns the information as a data table shown below as Table IV 2 Table IV 2 Inspection Statistics for SIC 2047 Dog and Cat Food Manufacturing in FY 2011 Organized by Most Frequently Cited Standard L aceon general use 19100095 Ears 1428 Occupational noise exposure em gt t o 2 19100242 1250 Hand and portable powered tools and equipment o general Notes Standards are presented as eight character part section levels consisting of the part number followed by the standard number Standard numbers less than 1000 require leading zeros 1910 95 becomes 19100095 Respiratory protection For the row labeled Total the value i
182. onsidered the last option for controlling noise exposures HPDs are generally used during the time it takes to implement engineering or administrative controls or when such controls are not feasible Unless great care is taken in establishing a hearing conservation program workers will often receive very little benefit from HPDs The best hearing protector when fitted correctly is one that is accepted by the worker and worn properly If the worker exposure is above 85 dBA 8 hour TWA hearing protection must be made available along with the other requirements in the hearing protection program Earplugs come in a variety of sizes shapes and materials and can be reusable and or disposable Figure 10 Earplugs are designed to occlude the ear canal when worn All hearing protectors are provided with an NRR Although earplugs can offer protection against the harmful effects of impulse noise and some earplugs are designed specifically to reduce this type of noise the NRR is based on the attenuation of continuous noise and may not be an accurate indicator of the protection attainable against impulse noise Earplugs are better suited for warm and or humid environments such as foundries smelters glass works and outside construction in the summer Figure 10 Earplugs Section II Chapter 5 Page 44 Earmuffs are another type of hearing protector Figure 11 They come in a variety of sizes shapes and materials and are relatively easy to disp
183. ontour map which is often useful because it provides a simple representation of the sound field over a large area Besides identifying regions of lower noise levels these maps may also be used to visually educate and train workers regarding where hearing protection is mandatory and as a tool for identifying hot spots for potential noise controls 3 Administrative Controls Administrative controls defined as management involvement training of workers and changes in the work schedule or operations that reduce noise exposure may also effectively reduce noise exposure for workers Examples include operating a noisy machine on the second or third shift when fewer people are exposed or shifting a worker to a less noisy job once a hazardous daily noise dose has been reached Generally administrative controls have limited use in industry because workers are rarely permitted to shift from one job to another Be aware that if noise levels are high enough rotation could increase the chances of hearing loss in more workers If there is a regular noise level of 90 dB for example a healthy worker in the area can rotate into an area with a 50 dB noise level without a substantial increase in risk of hearing loss Another administrative control involves redesigning workers work schedules to reduce the amount of time that any one worker is located in the hazard area To increase the effectiveness of this control employers can also ensure that noise expo
184. or shield the receiver from the direct sound transmission path For a partial barrier to be effective it is critical that the receiver be in the direct field not the reverberant field Should the worker s location be primarily in the reverberant field then the benefit of the barrier will be negligible The noise reduction provided by a barrier is a direct function of its relative location to the source and receiver its effective dimensions and the frequency spectrum of the noise source The practical limits of barrier attenuation will range from 15 to 20 dB For additional details on calculating barrier insertion loss or attenuation the user should review some of the references particularly The Noise Manual AIHA 2003 or latest edition Recommendations for acoustical barrier design and location to maximize noise reduction capabilities include e The barrier should be located as close as practical to either or both the source and receiver e The width of the barrier on either side of the noise source should be at least twice its height the wider the better e The height should be as tall as practical e The sound transmission loss of the panel should be at least 10 dB greater than the estimated noise reduction of the barrier e The barrier should be solid and not contain any gaps or openings e The worker s being protected by the barrier should work primarily in the direct sound field iii Receiver Treatment The final control opt
185. oratory IV Investigation Guidelines A workplace noise investigation typically involves e Advance planning including determining whether sound levels at the site might be hazardous e Reviewing employer records Reviewing the Hearing Conservation Program and audiograms Reviewing the OSHA 300 Log for hearing loss cases Determining if workers have hearing loss e Conducting the walkaround evaluation Identifying the sources of noise Documenting noise levels Conducting follow up monitoring Determining the noise s potential effect on workers e Evaluating the employer s efforts to protect workers hearing hazard abatement and control In some workplaces your visit will be the first time a thorough investigation has been performed frequently however at least some aspects of noise investigations will have been completed previously through the employer s workplace health and safety measures or sometimes as part of seemingly unrelated activities such as expanding operations or upgrading equipment To conduct an investigation you will need to determine what information is already available through employer or industry records and then confirm it and fill in the gaps To ensure that the investigation is efficient however you must be prepared to accomplish both these steps simultaneously which requires some advance planning Section III Chapter 5 Page 60 A Planning the Investigation An effective noise inves
186. ording each reading in sequence Variable frequency sounds and sounds that constantly vary in intensity present a challenge to frequency analysis Unless the sound is relatively constant throughout the process of evaluating all frequency bands it might not be possible to obtain an accurate reading The CSHO should attempt to determine whether cyclic sounds have a stable period during which readings would be more accurate Section III Chapter 5 Page 55 4 Noise Dosimeter Like a sound level meter a noise dosimeter can measure sound levels However the dosimeter is actually worn by the worker to determine the personal noise dose during the workshift or sampling period Figure 21 Noise dosimetry is a form of personal sampling averaging noise exposure over time and reporting results such as a TWA exposure or a percentage of the PEL Dosimeters can be used to e Make compliance measurements according to Oregon OSHA s Noise standard e Measure the worker s exposure to noise over a period of time e g a task or an entire workshift and automatically compute the necessary noise dose calculations Increasingly some sound level meters can function as noise dosimeters although they are larger than typical dosimeters while many noise dosimeters provide instantaneous sound level readings in decibels and therefore can be used as Type 2 sound level meters Figure 21 Noise Dosimeter i Noise Dosimeter Type
187. organizations will find that hearing conservation program costs average 350 to 400 per program participant per year General guideline 2 Workers compensation costs for hearing loss average about 0 2 of payroll Workers compensation averages about 2 of payroll 10 percent of that is associated with hearing loss compensation General guideline 3 Reducing compressed air pressure and volume used can reduce noise levels substantially and can also save on energy costs It is almost always cost effective Other good opportunities for noise reduction are associated with routine maintenance and machine guarding why not build in noise reduction at the same time General guideline 4 As a criteria for an acoustical maintenance program each machine should typically operate within 2 dBA of the minimum sound level of which it is optimally capable Sources Driscoll 2010 2012 Several sources have offered more detailed methods for evaluating the costs of noise and benefits of noise control These methods involve diverse interpretations of how the costs of noise exposure are calculated based on the individual needs of the organization for which the method was developed They also include various additional steps and tools to help refine the organization s priorities or to help standardize the process Section V C Economic Feasibility of Noise Control Engineering presents one method for evaluating the feasibility of noise engineering contr
188. osimeter reading and provide insight into how and when exposure is occurring Some noise dosimeters log data that can be downloaded to a computer and later graphed against time to show how the worker s noise exposure varies over the course of a shift This is a useful feature but is not a substitute for good notes on the workplace and the sources of noise in specific times and places Figure 23 Microphone Positioning and Wind Screen Use Section II Chapter 5 Page 59 The Oregon OSHA Laboratory maintains the following specialized noise analysis equipment which can be used for noise exposure and engineering control evaluations Sound Level Meter and Octave Band Analyzer The Oregon OSHA Laboratory maintains multipurpose Type I sound level meters and octave band analyzers which can also be operated as sound intensity analyzers for identifying noise sources and determining engineering controls In addition this equipment includes a building acoustics system for measuring noise decay and determining the reverberation characteristics for a given room Based on the noise decay data calculations can be performed to estimate potential noise reduction if absorptive materials are applied to room surfaces such as the walls and ceiling Specialized Noise Dosimeters Super duty noise dosimeters that are contained in a sealed waterproof intrinsically safe metal housing are currently not available through the Oregon OSHA Lab
189. ost of 0 015 U S Dollars per 1 Nm hr and an estimated use time of 40 this equates to 704 hours of consumption per year Therefore the annual cost for the open pile is 185 Nm hr x 0 015 x 704 hours 1953 60 Pneumatic and Compressed Air Systems And there is an energy cost savings too Next using a Silvent 705 quiet design nozzle provides the same air flow service but only uses 95 Nm hr This results in an annual cost of 1003 20 Therefore the savings is Open Pipe Quiet Design Nozzle Annual Savings 1953 60 1003 20 950 40 Per Nozzle AND provides 20 dBA of attenuation Section III Chapter 5 Page 169 Pneumatic and Compressed Air Systems Manufacturers of quiet design compressed air devices Silvent Inc Exair Corporation Vortec Allied Witan Company McGill Air Pressure Corp Pneumatic and Compressed Air Systems Contact any number of these manufacturers and 1 Request a free of charge survey and audit of all compressed air devices used at the plant 2 Recommendations and cost estimates for retrofitting all air sources 3 Calculation of the energy savings and break even point for retrofit investment Section III Chapter 5 Page 170 Pneumatic and Compressed Air Systems Summary Steps for minimizing compressed air noise 1 Optimize air pressure settings for all pneumatic devices document and maintain settings over time Identify and repair compressed air lea
190. osure can contribute to other physical effects These can include muscle tension and increased blood pressure hypertension Noise exposure can also cause a stress reaction interfere with sleep and cause fatigue Section II Chapter 5 Page 21 F Ultrasonics Ultrasound is high frequency sound that is inaudible i e cannot be heard by the human ear However it still might affect hearing and produce other health effects For more information see Appendix C Factors to consider regarding ultrasonics include e The upper frequency of audibility of the human ear is approximately 15 to 20 kilohertz kHz This is not a set limit some individuals may have higher or lower usually lower limits The frequency limit normally declines with age e Most of the audible noise associated with ultrasonic sources such as ultrasonic welders or ultrasonic cleaners consists of subharmonics of the machine s major ultrasonic frequencies Example Many ultrasonic welders have a fundamental operating frequency of 20 kHz a sound that is at the upper frequency of audibility of the human ear However a good deal of noise may be present at 10 kHz the first subharmonic frequency of the 20 kHz operating frequency which is audible to most people G Noise and Solvent Interactions Animal experiments have indicated that combined exposure to noise and solvents induces synergistic adverse effects on hearing Experimental studies have explored specifi
191. ot Sources NIOSH 1979 Cox and D Antonio 2004 Dense heavy materials typically have low absorption coefficients 1 e they reflect a high percentage of the sound energy Because they do not absorb much sound energy they do not transmit much sound and little sound penetrates through them ii Reducing Noise Transfer Across Barriers Using Sound Transmission Loss Materials Table V 3 and V 4 show various transmission loss values for common building materials at specific frequencies and material thicknesses Note that the values in these tables are measured under ideal laboratory conditions as a resource for comparing different materials In the workplace the noise exposure experienced by the receiver would not actually be reduced by the reported transmission loss value because imperfections in enclosures barriers or other noise controls made of these materials permit sound to go around the material leak through cracks or utility paths or pass through other materials with lower transmission loss values e g a door jamb window glass that were also used in construction Table V 3 demonstrates how the thickness of two materials plywood and steel influences the transmission loss values for the materials and Table V 4 compares the relative transmission loss values for common building materials Section III Chapter 5 Page 82 Table V 3 Effect of Thickness on Transmission Loss Values for Plywood and Steel dB C aa 128
192. otoxicol Teratol 21 6 689 97 Lund S P and G B Kristiansen 2008 Hazards to Hearing from Combined Exposure to Toluene and Noise in Rats Int J Occup Med Environ Health 21 1 47 57 Maguin K P Campo and C Parietti Winkler 2009 Toluene Can Perturb the Neuronal Voltage Dependent Ca Channels Involved in the Middle Ear Reflex Toxicol Sci 107 2 473 81 Section III Chapter 5 Page 131 M kitie A A U Pirvola I Pyykk H Sakakibara V Riihim ki and J Ylikoski 2003 The Ototoxic Interaction of Styrene and Noise Hear Res 179 1 2 9 20 Morata T C 1989 Study of the Effects of Simultaneous Exposure to Noise and Carbon Disulfide on Workers Hearing Scand Audiol 18 53 8 Morata T C D E Dunn L W Kretschmer G K Lemasters and R W Keith 1993 Effects of Occupational Exposure to Organic Solvents and Noise on Hearing Scand J Work Environ Health 19 245 54 Morata T C A C Johnson P Nylen E B Svensson J Cheng E F Krieg A C Lindblad L Ernstgard and J Franks 2002 Audiometric Findings in Workers Exposed to Low Levels of Styrene and Noise J Occup Environ Med 44 806 14 Morioka I N Miyai H Yamamoto and K Miyashita 2000 Evaluation of Combined Effect of Organic Solvents and Noise by the Upper Limit of Hearing Ind Health 38 2 252 7 Muijser H J H Lammers and B M Kullig 2000 Effects of Exposure to Trichloroethylene and Noise on Hearing in Rats Noi
193. oustical Maintenance Successful implementation of an acoustical maintenance program will ensure the correction of simple and often overlooked noise problems This process alone will yield significant benefits in both the long term life of the equipment and minimizing the noise exposure risk to employees Machine Guarding If you must guard then let s go all the way Section IH Chapter 5 Page 177 Machine Guarding and Acoustical Benefits Poly Carbonate Safety Enclosures Seal off all small gaps and openings along all polycarbonate panel edges and the adjacent framework and the bottom edge of the machine cabinet to the floor Machine Guarding and Acoustical Benefits DECREASE IN THE NOISE REDUCTION DUE TO SMALL OPENINGS IN ENCLOSURE PANELS Example The transmission loss of a C_ wall with a potential TL of 38 dB will be reduced to 29 d8 with only a 0 1 percent area leak s amp A N a tt a pets ACTUAL TRANSMISSION LOSS dB POTENTIAL TRANSMISSION LOSS dB Section III Chapter 5 Page 178 Machine Guarding and Acoustical Benefits Tubular rubber trim along edges available fronr Trim Lok Ince www trimlok com Machine Guarding and Acoustical Benefits NOISE REDUCTION RESULTS SOUND LEVELS BEFORE amp AFTER ELIMINATION OF GAPS Overall Noise Reduction 10 4 dBA Before Treatment 94 6d8BA rA After Treatment 84 2 dBA SOUND LEVEL dBA D o co
194. ovoke irreversible hearing impairment with the cochlear hair cells organ of Corti being considered a target tissue for these solvents Figure 5 Campo et al 2007 Scanning electron micrograph of a rat organ of Corti prior to left panel and after right panel toluene exposure from European Agency for Safety and Health 2009 as published in Lataye et al in 1999 Although the cochlea suffers damage particularly during co exposure recent studies have reported that solvents reduce the protective role played by the middle ear acoustic reflex an involuntary muscle contraction that normally occurs in response to high intensity sound stimuli A disturbance of this reflex would allow more acoustic energy into the inner ear Campo et al 2007 Lataye et al 2007 Maguin et al 2009 A number of epidemiological studies have investigated the relationship between hearing impairments and co exposure to both noise and industrial solvents Chang et al 2003 De Barba et al 2005 Johnson et al 2006 Kim et al 2005 Morata 1989 Morata et al 1993 2002 Morioka et al 2000 Prasher et al 2005 Sliwinska Kowalska et al 2003 2005 Due to confounding factors straightforward conclusions could not easily be drawn from these studies However the evidence of additive or synergistic ototoxic effects due to combined exposure to noise and solvents is very strong Lawton et al 2006 Hoet and Lison 2008 A recent longitudi
195. ples of source relocation e Rerouting all pneumatic or compressed air discharge ports from outside to the inside of machine cabinets e Using pipe extensions to relocate pneumatic exhausts away from the immediate area and into unoccupied spaces e Locating blowers e g dust collectors vacuum pumps on the building roof or in routinely unoccupied areas and using extended ductwork to service the process or equipment of concern e Conducting reclaim or material scrap grinding in routinely unoccupied areas ii Path Treatment Assuming that all available options for controlling noise at the source have been exhausted the next step in the noise control hierarchy is to determine ways to treat the sound transmission path Typical path treatments include adding sound absorption materials to the room or equipment Section III Chapter 5 Page 39 surfaces installing sound transmission loss materials between the source and receiver s using acoustical enclosures or barriers or any combination of these treatments A description of each treatment option follows Sound Absorption Materials Sound absorption materials are used to reduce the buildup of sound in the reverberant field The reverberant field exists at all locations where sound waves reflect off relatively hard surfaces such as walls ceilings or inside enclosures and then combine with the sound waves propagating directly from the noise source The added effect produces a higher n
196. ployment frequency and duration of noise exposure on the appropriate OSHA form f Explain to the workers that you will be checking the noise dosimeter throughout the day to ensure that the microphone is oriented properly and taking direct reading measurements with your SLM in their hearing zone g Record the time you turned on the noise dosimeter s 3 During dosimeter sampling to evaluate the noise hazard s document the following types of noise inspection data for each worker sampled a Take at least 10 periodic SLM measurements in each sampled worker s hearing zone and obtain and note SLM readings A and C weighted during different phases of the work performed by the worker during the shift Take enough readings to identify work cycles and the contribution of different noise sources from machine s and or processes Take notes to identify the level of each noise source fully document on appropriate OSHA form A and C readings will assist in determining noise control measures Octave band readings are a better alternative Examples of noise sources might include adjacent workers machines compressed air blow off and metal on metal from punching sawing drilling hydraulics electric motors rollers parts falling into bins and grinders More readings should be taken when noise levels fluctuate widely Hone in on noise sources by following noise gradients take note of where SLM levels increase It is often possible to identify th
197. portant to account for the time during the workday that a worker was not exposed to noise hazards At the time using a 5 dB exchange rate was viewed as a sufficient way to account for this In 1974 OSHA published a proposed occupational noise standard which included a requirement for employers to provide a hearing conservation program for workers exposed to an 8 hour TWA of 85 dBA or more This provision was adopted as part of the amendments of 1981 and 1983 The 8 hour TWA for OSHA s noise standard remained at 90 dBA with a 5 dBA exchange rate and included a requirement for a hearing conservation program for workers exposed to an 8 hour TWA of at least 85 dBA While OSHA provided requirements for hearing conservation programs in general industry the construction industry standard remained less specific in that regard More recently in the 2002 recordkeeping standard 29 CFR Part 1904 OSHA clarified the criteria for reporting cases involving occupational hearing loss In 1979 the U S Environmental Protection Agency EPA developed labeling requirements for hearing protectors which required hearing protector manufacturers to measure the ability of their products to reduce noise exposure called the noise reduction rating NRR OSHA adopted the NRR but later recognized that the NRR listed on hearing protectors often did not reflect the actual level of protection which likely was lower than indicated on the label because most workers were not pro
198. pproximately 100 professional industrial hygienists were given an opportunity to complete a worksheet on the costs of the HCP at their organizations This exercise was part of a workshop on the economics of noise control engineering versus the hearing conservation program Driscoll 2010 The worksheet results were quite consistent in showing that using these 18 points as cost criteria the majority of organizations spent 350 to 400 per year per worker in the hearing conservation program Results for a few organizations however were substantially higher The highest costs tended to be associated with fixed daily fees for services provided at multiple Section III Chapter 5 Page 138 remote locations where few workers were employed the highest hearing conservation program cost reported was 1 800 per worker per year Costs were lower when these fixed fees such as for audiometry van service to remote facilities could be averaged over a larger number of workers However in general the total hearing conservation program cost was not notably different for small organizations compared with large organizations In its next edition estimated in 2013 AIHA s The Noise Manual will be updated to include some of these points G 1 3 Example Colgate Palmolive Winner of the 2012 Safe In Sound Award NIOSH has partnered with the National Hearing Conservation Association NHCA to create an award for excellence in hearing loss prevention This aw
199. pter 5 Page 4 TABLE OF CONTENTS CONTINUED C Economic Feasibility of Noise Control Engineering 93 l Back round resisae e ea E a eae eae eee a 93 2 Assumptions for an Economic Analysis 94 3 General Principles reecissessseronsee dae rreri tennta 95 A Examples e ers seg deo sede Fem eae eee ants Bee in y S 95 VI REFERENCES oero 2505 Sap 6 ede ae aie e ee ees 102 VIL RESOURCES ceio bot ch den heri miaa hee ATAN REE RTE teers 105 A Reference Books and Articles nennuuuauua cece e eee 105 1 Comprehensive Review Noise Hearing Loss Noise Control 105 2 Control and Engineering 2542154 casucend lt idee ene ceaenand 106 B Noise PHYSICS 225 42204 8 4 04 Ga beedeaendrto eae ebeeedaeaer es 107 C Hearing LOSS 32404 seayeadee se dadeee oe ee boee ade eed 107 1 Hearing Loss Reporting 0 0 e eee eee 107 2 Hearing Loss Incident Rates 0 000000 00 08 107 3 Hearing Loss Prevention 2 2406sn0sVes race tau eeods 107 D Sound Levels of Equipment Occupations and Activities 108 E Noise Control isi s03 444d aeeaded cava 4054 bs tala en eedgaes 108 1 Engineering Controls and Noise Control Programs 108 2 Noise Control Products 2 20 2 necseseneeaedeseer ens 109 3 Quiet and Quiet by Design Programs 4 109 F Cost of Hearing Loss Cost of Hearing Conservation Programs 109 G Acoustical Consultants 0 0
200. quates to an average cost of 400 per worker Many of these projects also resulted in energy savings cleaner facilities and improved equipment life One of Colgate Palmolive s goals is to create a Zero Hearing Protection site Because the company uses the ACGIH TLV criteria i e 85 dBA with 3 dBA doubling rate or the local regulation whichever is more stringent this goal will reduce worker noise exposure to levels well below OSHA s permissible exposure limit PEL and action level AL Section III Chapter 5 Page 139 In an online presentation Colgate Palmolive provides a photojournal of noise control projects and reports on the dBA levels before and after modifications View this presentation here G 2 NASA Buy Quiet Roadmap NASA developed a comprehensive program to guide quieter equipment purchases This program termed the Buy Quiet Process Roadmap is part of the NASA EARLAB Auditory Demonstration Laboratory website General guidelines General guideline 1 The cost of a dual ear full disability claim across the United States reported in The Noise Manual Berger et al 2003 averages approximately 66 000 in 2011 dollars assuming a long term average of 4 2 inflation General guideline 2 The net present value of the hearing conservation program and personal protective equipment hearing protective devices may be set to 0 for TWAs below the AL Source Nelson 2012 The Roadmap includes a simple spreadsheet
201. r during the period selected In most industrial settings the meter fluctuates less and therefore is easier to read when measurements are made with the slow response rather than the fast response A rapidly fluctuating sound generally yields higher maximum sound pressure levels when measured with a fast response The choice of meter response depends on the type of noise being measured the intended use of the measurements and the specifications of any applicable standards For typical occupational noise measurements including extremely elevated short term noise e g noise that will be compared to the 115 dBA maximum for a 15 minute period the meter response on a sound level meter should be set at slow For more information on OSHA s standard for extremely elevated short term noise exposures see Section II 2 OSHA Noise Standards Many sound level meters also have peak and impulse response settings for measuring transient sounds sounds that decay or pass with time These settings are not interchangeable the true peak value is the maximum value of the noise waveform while the impulse measurement is an integrated measurement It is appropriate to use the true peak reading only when determining compliance with Oregon OSHA s 140 dB peak instantaneous sound pressure level 29 CFR 1910 95 b 1 or 29 CFR 1926 52 e Avoid using the impulse response setting when measuring true peak sound pressure levels Note that noise dosimeters and soun
202. r of a hearing conservation program the engineering option is economically feasible 2 Consider the situation where the planer has been relocated to a room by itself The room is treated with acoustical material to prevent reflected or reverberant noise Both workers who operate the planer are administratively controlled to prevent their noise doses from exceeding 100 dBA The planer is operated on the second shift only The employer s records indicate that the hearing conservation program costs a little more than the initial estimate an average of 419 per year per worker Are either of the two engineering control options for the planer described in the previous paragraphs economically feasible The per worker cost of hearing conservation is 419 x 2 938 per year for hearing conservation This cost for hearing conservation is compared to the per year cost of the two engineering options rebuild and upgrade the planer at an average cost per year of 1 000 or construct an enclosure around the planer within the room at an average cost per year of 681 Section III Chapter 5 Page 99 Since the 681 cost per year of constructing an enclosure is less than the 938 cost per year of the hearing conservation program this engineering option is economically feasible iii Tables for Economic Analysis Examples Tables V 5 and V 6 provide background information used in the examples for economic feasibility determinations Table V 5 Hearin
203. re Safety and Health Topics Occupational Safety and Health Administration OSHA No date Noise and Hearing Conservation Noise and Hearing Conservation eTool Occupational Safety and Health Administration OSHA Driscoll 2002 Noise and Hearing Conservation Noise and Hearing Conservation eTool Occupational Safety and Health Administration Produced under contract by Dennis Driscoll OSHA 1980 Noise Control A Guide for Workers and Employers Publication Number 3048 engineering control sections only Occupational Safety and Health Administration OSHA 1982 Standard Interpretation Letter to Mr Jonathan A Jacoby from OSHA 26 March Question of whether the noise standard is adjusted for workshifts greater than 8 hours 1910 95 OSHA 1987 Standard Interpretation Use of Walkman Radio Tape or CD Players and Their Effect When Hearing Protection is in Use 1910 95 2 1910 95 2 ID OSHA Region HI 2001 Enforcement of the Occupational Noise Exposure Standards 29 CFR 1910 95 1926 52 and 1926 101 Inspection Procedures and Interpretive Guidance including Appendix C Economic Feasibility of Noise Control Engineering and Table 5 6 Noise Control Engineering Cost Assumptions Directive Number STD 1 4 1A July 19 OSHA 1997 Standard Interpretation Placement of the noise dosimeter microphone for measuring the noise exposure of an employee using an airline respirator equipped with a shroud 1910 95 Sect
204. rected threshold shift 6 bo p The age corrected average is 6 9 8 3 7 66 Since this is less than 10 no STS has occurred Example 3 Selected audiometric test data for a 35 year old female worker with 10 years of service Test Frequency Left Ear Hz Test Frequency Right Ear Hz year 1 000 2 000 000 a000 6 000 000 2 000 3 000 s 00 6 000 Bacinels o hs ha fis fe hs hs h fs year For the left ear the shifts at the required frequencies are 10 dB 9 dB and 9 dB respectively No STS can occur because the average is less than 10 dB For the right ear the values are 9 dB 12 dB and 19 dB 9 12 19 3 13 33 Since the average is greater than or equal to 10 dB the age correction values need to be applied Age Correction Values for Females from Table F 1 in Appendix F of 1910 95 OOOO o poom poo oo E ss Si Difference in age correction 1 values Age Corrected Threshold Shift Current Year Age 35 Right Ear foe i pie et B 2 000 3 000 4 000 Threshold shifts from baseline o e Difference in age correction values Age corrected threshold shift s o bo The average threshold shift is 8 9 16 3 11 Since the average shift is greater than or equal to 10 dB an STS has occurred even though two of the values are less than 10 Also note that the worker s current average hearing threshold for the right ear is 24 27 30 3 27 Since this exceeds 25 both conditions are met an STS has occurred and the hearing th
205. reshold for the right Section II Chapter 5 Page 158 ear is greater than or equal to 25 dB therefore the case is recordable Review the OSHA 300 Log to determine whether the case was recorded Example 4 Selected audiometric test data for a 40 year old male worker F 1 000 2 00 3 00 300 6 000 1 000 2 00 3 00 a0 s 000 ren s h e b amp b b kh bb asas gt b b bh bo k k b hb meso ha p p o oo e a a o aoo meas p fis fo hs po fie hs jo hi fs Review the data and observe that the lowest thresholds for the left ear occur in the second audiogram at 2 000 3 000 and 4 000 Hz Use age 25 as the baseline for the left ear For the right ear use the first audiogram as the baseline because it has the lowest thresholds Next compare the current year audiogram with the baseline Observe that for each ear at the required frequencies all changes in threshold exceed 10 dB so the averages will exceed 10 dB for each ear The age correction factors must now be applied to determine whether an STS occurred Age Correction Values from Table F 1 in Appendix F of 1910 95 e h ja Difference in age correction E a gt gt gt ge a a 10 10 AININ as E E e a o E e A A S h Ja m1 SIS n gt l l gt a as gt gS a Js ey lt es E f oO nA ki e gt oO D Difference in age correction lt S e f oO Nn a ya i too Q D a gt Test Frequency Le
206. ribe the qualities of sound These qualities influence how it affects hearing and health how it is measured and how it can be controlled Effective occupational noise investigations require the investigator to understand these basic terms B Basic Qualities of Sound 1 Wavelength The wavelength A is the distance traveled by a sound wave during one sound pressure cycle as shown in Figure 2 The wavelength of sound is usually measured in meters or feet Wavelength is important for designing engineering controls For example a sound absorbing material will perform most effectively if its thickness is at least one quarter the wavelength Figure 2 Wavelength Section III Chapter 5 Page 8 2 Frequency Frequency f is a measure of the number of vibrations i e sound pressure cycles that occur per second It is measured in hertz Hz where one Hz is equal to one cycle per second Sound frequency is perceived as pitch i e how high or low a tone is The frequency range sensed by the ear varies considerably among individuals A young person with normal hearing can hear frequencies between approximately 20 Hz and 20 000 Hz As a person gets older the highest frequency that he or she can detect tends to decrease Human speech frequencies are in the range of 500 Hz to 4 000 Hz This is significant because hearing loss in this range will interfere with conversational speech The portions of the ear that detect frequencies betw
207. ry World Health Organization No date Engineering Noise Control VII Resources A Reference Books and Articles 1 Comprehensive Review Noise Hearing Loss Noise Control American Industrial Hygiene Association 2003 The Noise Manual 5th edition Edited by E H Berger et al Fairfax VA American Industrial Hygiene Association A comprehensive manual on noise hazard and control for industrial hygienists and safety professionals A revised edition is anticipated in 2013 Section III Chapter 5 Page 105 Dobie Robert A 1993 Medical Legal Evaluation of Hearing Loss Van Nostrand Reinhold Extensive information on occupational hearing loss Sataloff R T and Sataloff J 1993 Occupational Hearing Loss Second Edition Marcel Decker Inc Detailed information regarding occupational hearing loss Suter A H 2002 Construction Noise Exposure Effects and the Potential for Remediation a Review and Analysis AIHA Journal 63 768 789 November December Noise Control and Engineering Investigators develop new products and applications for noise control however the principles and basic materials of noise control remain unchanged Some earlier titles remain useful Books can be obtained through new or used book sellers and through interlibrary loan programs Barron R F 2003 Industrial Noise Control and Acoustics New York NY Marcel Dekker Inc Bell L H and D H Bell 1994 Industrial Noise Control Fundament
208. s According to Oregon OSHA s Noise standard 29 CFR 1910 95 the noise dosimeter is the primary instrument for making compliance measurements Before use the dosimeter must be set up to record noise exposure using the following criteria e Exchange rate 5 dB e Frequency weighting A e Response slow e Criterion level 85 dBA Hearing Conservation or 90 dBA Administrative and Engineering Controls e Threshold 80 dBA Hearing Conservation or 90 dBA Administrative and Engineering Controls As noted above some dosimeters can simultaneously record exposure using two sets of criteria With these instruments the CSHO can obtain separate noise exposure levels based on both the 80 dBA and the 90 dBA threshold Other noise dosimeters that lack this feature must be set to record using one of these thresholds or the other In addition to the 8 hour TWAs Oregon OSHA s noise standards list a short term level of 115 dBA for a 15 minute period which is not to be exceeded this is for steady state sounds measured on the slow response setting Although sound this loud is unusual some dosimeter models indicate when the maximum allowable sound level of 115 dBA has been exceeded This signal should not be used for compliance determination however because it might not take the duration of the exposure to this noise level into consideration But noise that exceeds 115 dBA should be incorporated into the overall TWA noise exposure determination see
209. s find the ratio of the intensity Z of sound to the threshold intensity Io dB 10 I logio Z Io Layg or LAVG The average sound level measured over the run time of measurement This becomes a bit confusing when thresholds are used because the average does not include any sound below the threshold Sound is measured in the logarithmic scale of decibels so the average cannot be computed by simply adding the levels and dividing by the number of samples When averaging decibels short durations of high levels can significantly contribute to the average level Example Assume the threshold is set to 80 dB and the exchange rate is 5 dB the settings of OSHA s Hearing Conservation Amendment Consider taking a 1 hour noise measurement in an office where the A weighted sound level was typically between 50 dB and 70 dB If the sound level never exceeded the 80 dB threshold during the 1 hour period then the LAVG would not indicate any reading at all If 80 dB was exceeded for only a few seconds due to a telephone ringing near the instrument then only those seconds will contribute to the LAVG resulting in a level perhaps around 40 dB notably lower than the actual levels in the environment LDN Representing the day night sound level this measurement is a 24 hour average sound level where 10 dB is added to all of the readings taken between 10 p m and 7 a m This is primarily used in community noise regulations where there is a 10 dB penal
210. s and Performance Most noise dosimeters operate with the precision and accuracy of a Type 2 sound level meter Therefore the variations in dosimeter types are primarily a function of either the physical form or the analytical features of each model Historically the typical noise dosimeter has included a small positionable microphone connected to the dosimeter by a thin cable The microphone sits in the worker s hearing zone e g shoulder or lapel near the ear while the dosimeter clips to the worker s belt Advances in miniature electronics and wireless technology however have permitted manufacturers to offer similar capabilities in a wider range of physical forms e g wireless microphones that clip to the worker s shoulder and transmit information back to a base station miniature microphones that measure sound levels in the worker s ear Section HI Chapter 5 Page 56 Function also varies Simple dosimeters record a single channel and report basic dosimetry results More complex models can record as if they were three or four separate dosimeters each integrating the sound level over time using different criteria e g 3 dB and 5 dB exchange rates different threshold settings Noise dosimeters are subject to the same sensitivity to temperature and humidity as sound level meters Although some have water resistant housings they should still be treated as sensitive electronic instruments and be protected from moisture and physical imp
211. s develop hearing conservation programs conduct noise evaluations measure sound levels and perform noise dosimetry In the box for Specialty select Hearing Conservation Noise Reduction Associations Education and Conferences Institute of Noise Control Engineering Sponsor of the annual conference Inter Noise International Congress and Exposition on Noise Control Engineering Offers continuing education National Council of Acoustical Consultants The acoustician seeks to understand and quantify the production control transmission and effects of sound Offers continuing education Acoustical Society of America International scientific society in acoustics dedicated to increasing and diffusing the knowledge of acoustics and its practical applications Offers continuing education Section III Chapter 5 Page 110 Council for Accreditation in Occupational Hearing Conservation Offers continuing education Acoustical Solutions Inc ASI University This noise control materials manufacturer s website offers general background information on understanding noise control principles and terminology Offers continuing education related to noise through the American Institute of Architects Section III Chapter 5 Page 111 APPENDIX A Glossary A weighting A measurement scale that approximates the loudness of tones relative to a 40 dB sound pressure level 1 000 Hz reference tone A weighting is said to bes
212. s illustrated in Figure 27 A worker can bend a piece of metal by hitting it with a hammer and applying a large amount of force over a short period of time or by applying the same force with the pliers over a longer time period thereby reducing the noise Section III Chapter 5 Page 71 Figure 27 Reducing Driving Force YA flat Strip of meta can be bent noi ily with a hammer ii Reduce High Velocity of Fluid Flow Fluid whether air or liquid that moves through vents valves and piping at high velocities can generate noise due to turbulence Figure 28 shows that installing softer bends in the pipe and increasing the distance between the valves will reduce the turbulence in the line and consequently reduce the noise generated This solution takes up more space and is often not possible in a process However it is sometimes possible in air ejection processes to reduce the required velocity of the air flowing from the nozzle by increasing the accuracy of the aim of the nozzle Often large pressure drops across valves which cause noise can be prevented with in line diffuser silencers which reduce the pressure upstream of the valve Installing a muffler on the end of the nozzle is another option All these methods can help reduce noise from compressed air sources For additional information see Appendix K Three Ways to Jump Start a Noise Control Program Section III Chapter 5 Page 72 Figure 28 Reducing Turb
213. s many years the recent decade is well represented 58 297 27 of the personal noise exposure levels in IMIS were measured in 2000 or later Table H 2 through II 5 summarize the noise measurements obtained by OSHA in each major industry sector These tables also present the median noise levels and the percentage of noise measurements over either the action level AL 85 dBA or the permissible exposure limit PEL 90 dBA The data appear in separate tables because OSHA uses different criteria for the AL and PEL Each noise measurement entered into IMIS is related to either the AL or the PEL depending on the threshold level designated during dosimeter setup OSHA obtained the vast majority of IMIS noise exposure records in manufacturing facilities Manufacturing is among the loudest industries with 43 of the IMIS noise samples exceeding the PEL of 90 dBA time weighted average TWA In addition 47 of the samples taken in the construction industry exceeded the PEL The IMIS exposure records for the manufacturing industry are presented by three digit North American Industrial Classification System NAICS codes in two tables Table H 4 and H 5 relative to the AL and PEL respectively In addition to median decibels and percent over the PEL Table II 5 shows the distribution of manufacturing industry dosimetry measurements at the PEL and higher by decibel level Table II 2 Noise Measurements Exceeding the AL IMIS 1979 2006 R
214. s of Noise Control Figure 34 Isolated Structure Borne Noise internal damping Driscoll Principles of Noise Control Noise control by reducing structure borne vibration involves installing vibration mounts and providing proper lubrication and maintenance for equipment Regular maintenance ensures proper operation of equipment and is less expensive than other engineering controls this maintenance can include tightening belts and lubricating moving parts Structure borne vibration can also be reduced by isolating a vibrating piece of equipment if identified as the primary source of noise using vibration mountings or shock absorbers Figure 35 The picture on the left shows neoprene isolators while the picture on the right shows spring isolators Vibration isolation mounts are effective for reducing low frequency noise Section III Chapter 5 Page 78 Figure 35 Neoprene and Spring Vibration Isolators Driscoll Principles of Noise Control vi Substitute for the Source One way to reduce noise at the source is to replace noisy equipment with a quieter alternative Manufacturers are aware of noise issues on equipment and often offer quieter models When it comes time to replace equipment employers are increasingly considering noise level as one of the selection criteria Some employers develop buy quiet programs as part of purchasing policies to ensure that noise levels are taken into consideration 2 Path Tre
215. se exists predominantly between the eardrum and the headset Because of the amplification properties of the human ear the sound that exists inside the ear while wearing a headset is quite different from ambient levels A head and torso simulator HATS is a head and shoulder mannequin with calibrated ears fitted with sophisticated acoustical sensing instrumentation Manufacturers produce HATS for various specialized purposes The HATS should match its intended purpose Probe microphones and similar devices allow sound levels to be measured inside the ear Most people however find that inserting a probe microphone into their ear canal is uncomfortable and object to wearing a probe for an 8 hour workday In addition a probe can damage the eardrum meaning that the person inserting it requires professional training For these reasons probe microphones should not be used for compliance purposes F 2 Methodology A method of monitoring worker exposure without invading the ear canal has been developed This sampling method evaluates the noise dose that a worker receives during the actual workday while wearing an insert type headset a monaural or binaural muff or a monaural or binaural foam headset The technique involves directly measuring the sound pressure level of a headset similar to the workers using a head and torso simulator HATS that can measure acoustic signals at the eardrum point The electrical signal input to the worker s heads
216. se Health 2 6 57 66 Prasher D H Al Hajjaj S Aylott and A Aksentijevic 2005 Effect of Exposure to a Mixture of Solvents and Noise on Hearing and Balance in Aircraft Maintenance Workers Noise Health 7 29 31 9 Sch per M P Demes M Zupanic M Blaszkewicz and A Seeber 2003 Occupational Toluene Exposure and Auditory Function Results From a Follow up Study Ann Occup Hyg 47 493 5025 Sch per M A Seeber and C van Thriel 2008 The Effects of Toluene Plus Noise on Hearing Thresholds an Evaluation Based on Repeated Measurements in the German Printing Industry Int J Occup Med Environ Health 21 191 200 Sliwinska Kowalska M E Zamyslowska Szmytke W Szymczak P Kotylo M Fiszer W Wesolowski and M Pawlaczyk Luszczynska 2003 Ototoxic Effects of Occupational Exposure to Styrene and Co exposure to Styrene and Noise J Occup Environ Med 45 15 24 Sliwinska Kowalska M E Zamyslowska Szmytke W Szymczak P Kotylo M Fiszer W Wesolowski and M Pawlaczyk Luszczynska 2005 Exacerbation of Noise Induced Hearing Loss by Co exposure to Workplace Chemicals Environ Tox Pharmacol 19 547 53 Section III Chapter 5 Page 132 APPENDIX E Noise Reduction Rating Noise Reduction Ratings When OSHA promulgated its Hearing Conservation Amendment in 1983 it incorporated the EPA labeling requirements for hearing protectors 40 CFR 211 which required manufacturers to identify the noise re
217. se Statistics i BLS Report on Hearing Loss in an Industry Reports of hearing loss by industry are summarized in BLS s Table SNRO8 Incidence Rates of Nonfatal Occupational Illness by Industry and Category of Illness This extensive table lists by industry the incidence of reported illnesses per 10 000 full time workers as shown on OSHA 300 Logs that employers are required to submit The table includes a column for hearing loss Comparing the hearing loss reporting rates in various industries will give you an estimate of the impact that noise has on the industry you are inspecting compared with other industries Note that variations in hearing loss reporting rates can influence the apparent incidence rate BLS publishes this information annually each fall covering the previous year s data Check for the latest edition of Table SNRO8 or for previous years tables at the Bureau of Labor Statistics web site Table IV 1 shows an example from BLS Table SNRO8 for NAICS 311111 Dog and Cat Food Manufacturing 12 8 of the 2009 reported occupational illnesses were related to hearing loss Section III Chapter 5 Page 61 Table IV 1 Example Incidence Rates of Nonfatal Occupational Illness Incidence rates per 10 000 full time workers 2009 Annual Skin Average Diseases NAICS Employment Total i Hearing All Other Industry Code Thousands Cases Poisonings Los Illnesses manufacturing Dog and cat food 311111 19 7 20 8 manufacturin
218. size of the surface area to be treated and the substrate thickness The supplier will then use the input data to select the most effective product for the particular application The vendor can also provide the buyer with estimates of noise reduction and costs for procuring the material Some common applications for vibration damping include e Hopper bins and product chutes e Resin pellet transfer lines provided they are metal pipe e Thin metal machine casings or panels that radiate resonant tones e Metal panels being impacted by production parts e g drop bins e Metal enclosure walls e Fan and blower housings e Gear box casings constrained layer damping required for thick substrates Vibration Isolation Most industrial equipment vibrates to some extent Determining whether or not the vibrating forces are severe enough to cause a problem is accomplished through a comprehensive noise and or vibration survey As machines operate they produce either harmonic forces associated with unbalanced rotating components or impulsive forces attributed to impacts such as punch presses forging hammers and shearing actions Excessive noise can be one result of the vibratory energy produced however potential damage to the equipment itself the building and or the product being manufactured is more likely Quite often vibration problems are clearly identified by predictive maintenance programs that exist within most industrial plants Assuming
219. sponsible for 25 33 of a plant s noise problems Compressed air noise is probably the easiest source to control Getting a handle on compressed air usage and noise can have significant financial and energy savings over time Section III Chapter 5 Page 164 Pneumatic and Compressed Air Systems Pneumatic or compressed air systems are used to Operate or motivate equipment using devices such as air cylinders air valves solenoids etc Air jets and nozzles including hand held air guns are used to move parts product blow off debris close flaps on corrugated containers boxes cases or similar service type actions Pneumatic and Compressed Air Systems Noise generated by compressed air is caused by turbulence due to the mixing of gases with widely different velocities Additional turbulence is created as the compressed air blows against objects such as parts or sections of the machinery Section III Chapter 5 Page 165 Pneumatic and Compressed Air Systems The shearing action occurring in the mixing region results in excessive noise where the sound level is proportional velocity of air flow raised to the 8th power Sound Level V Therefore the 1 Step toward controlling compressed air noise is to reduce the air velocity to as low as practical and maintaining that setting Noise Reduction Resulting from Air Pressure Adjustments 55 psig 122 dBA 30 psig 111 dBA 20 psig 103 dBA
220. ss prevention purposes engineering controls are defined as any modification or replacement of equipment or related physical change at the noise source or along the transmission path with the exception of HPDs that reduces the noise level at the worker s ear Engineering controls should be effective efficient and economical According to Federal OSHA CPL 2 2 35A Appendix A effective controls reduce noise levels by at least 3 dB Efficient controls should not cause extra hazards production problems or maintenance or sanitation issues Economical controls are cost effective for the employer discussed in Section B of this section Section III Chapter 5 Page 70 Pneumatic or compressed air systems e g air valves cylinders solenoids compressed air nozzles used in manufacturing are a major contributor to noise This type of noise is relatively easy to reduce with controls This section describes several types of engineering noise controls focusing on the different ways various materials can be used to reduce a receiver s noise exposure Noise is typically generated either by the surface motion of a vibrating solid material or by turbulence in a fluid including air All engineering control options either reduce the amount of noise generated by these events or interfere with the path between the noise source and the receiver A number of references on engineering controls are listed in Section VII Resources Some have been in use many
221. st operations e Do you know what the sources of noise are here e Where does the noise come from e What is your role in the hearing conservation program at this facility e Is there is list of departments included in the hearing conservation program e Do you do any training related to noise If so how is this accomplished e Do you have records that support your training on noise e What type of noise monitoring have you done Ask for copy of results e How often do you conduct audiometric testing on your workers e Do you keep audiometric test results To make sure your hearing conservation program is effective we will need to look at the audiometric test results for your workers to make sure everyone is included who needs to be e Can you think of anyone who has had an STS or has had some hearing difficulties Note Explain to the employer what an STS is e Do you have a list of those workers who had an STS during the past year e Who performs the audiometric testing Note Obtain name of company and address e Could we see copies of calibration of the audiometric booth if testing is conducted on site e What types of hearing protection are available e Is hearing protection required to be worn or voluntary e If required who enforces the use of hearing protection e Who conducts the training for hearing e Have you evaluated the attenuation of the hearing protection offered here e How are hearing losses recorded e
222. stream into another e Limit the fluid flow velocity to a maximum of 30 feet per second for liquids e Maintain laminar flow for liquids keep the Reynolds Number less than 2 000 e When vibratory energy is transferred to the pipe wall use flex connectors and or vibration isolation for the piping system and or acoustical insulation e When excessive noise in the fluid cannot be controlled by any of the options above install an in line silencer High Velocity Air Flow Pneumatic or Compressed Air Systems One of the most common noise sources within manufacturing equipment is pneumatic or compressed air driven devices such as air valves cylinders and solenoid valves High velocity air is also a major contributor to worker noise exposure where hand held air wands or guns are used to remove debris from work areas Finally compressed air nozzles are often used to eject parts from a machine or conveyor line All these forms of pneumatic systems generate undesirable noise as the high velocity air mixes with the atmospheric air creating excessive turbulence and particle separation It is important to note that the intensity of sound is proportional to the air flow velocity raised to the 8th power Therefore as a source modification it is recommended that the air pressure setting for all pneumatic devices be reduced or optimized to as low a value as practical As a general guideline the sound level can be reduced by approximately 6 dBA for each 30
223. sure can be reduced through various noise control methods Response Instruments that measure time varying signals are limited in how fast they can respond to changes in the input signal Sound dosimeters can operate with a wide variety of response times but the industry has chosen two particular response times to standardize measurements These are known as the slow and fast response times OSHA the Mine Safety and Health Administration and ACGIH all require the slow response for sound dosimetry The standardized time constant for the slow response is 1 second Section III Chapter 5 Page 115 Sound level meter An instrument that converts sound pressure in air into corresponding electronic signals The signals may be filtered to correspond to certain sound weightings e g A weighted scale C weighted scale Threshold level The A weighted sound level at which a personal noise dosimeter begins to integrate noise into a measured exposure For example if the threshold level on a sound level meter is set at 80 dBA it will capture and integrate into the computation of dose all noise in the worker s hearing zone that equals or exceeds 80 dBA Sound levels below this threshold would not be included in the computation of noise dose Use an 80 dBA threshold for measurements related to hearing conservation programs and a 90 dBA threshold for exposure results related to the need for engineering or administrative controls The hypothetical exposur
224. sure is kept to a minimum in nonproduction areas frequented by workers Select quiet areas to use as lunch rooms and work break rooms If these areas must be near the production line they should be acoustically treated Section III Chapter 5 Page 43 as describe elsewhere in this section to minimize background noise levels Employers can also increase the distance between workers and the noise source This can be accomplished in many ways For example television monitors allow the worker to monitor a job or process at a safe distance from the noise producing area a boom mounted drill increases the distance from the noise source to the worker Additionally noisy jobs on construction sites might be scheduled when other trades will not be affected Another administrative control involves creating policies that result in regularly scheduled equipment maintenance Maintenance should be scheduled frequently enough to minimize the noise produced by equipment with parts that are loose or not lubricated Regular maintenance should allow a piece of equipment to operate within 2 dBA of its lowest potential operating noise level Maintenance workers can also be trained to observe and listen for noise sources in equipment This might involve providing training on using sound level meters to perform surveys in work areas to identify areas with high noise levels 4 Personal Protective Equipment Hearing Protection Hearing protection devices HPDs are c
225. t e modifying equipment or facility design plans to reduce the sound level associated with the finished product than to purchase new production equipment Purchasing new production equipment is also typically cheaper than retrofitting existing equipment with noise controls Each facility must be responsible for evaluating which noise reduction options are most appropriate for it Facilities will have different options for significantly reducing noise levels at the lowest possible cost The following case studies provide a sample of engineering control options that have been effective and economically feasible for other facilities The studies are categorized by the engineering control technique involved Cost information is included when available 2 Engineering Control Case Studies i Acoustic Absorption Case study A fixed base router initially produced a noise level of 84 8 dBA in testing Workers placed 3M Thinsulate foam over the motor intake and exhaust vents After the foam was installed the router produced a noise level of 77 4 dBA approximately 8 dBA less than the original noise level The authors of this study estimated that it cost less than 1 per router to implement Koning et al 2003 Case study A company manufactures cement blocks in 8 10 and 12 sizes according to orders Cement fly ash and other raw materials are brought in on railcars and stored in silos The ingredients are then mixed and sent to the block mach
226. t In its early stages when hearing loss is above 2 000 Hz it affects the ability to understand or discriminate speech As it progresses to the lower frequencies it begins to affect the ability to hear sounds in general Section III Chapter 5 Page 19 The primary effects of workplace noise exposure include noise induced temporary threshold shift noise induced permanent threshold shift acoustic trauma and tinnitus A noise induced temporary threshold shift is a short term decrease in hearing sensitivity that displays as a downward shift in the audiogram output It returns to the pre exposed level in a matter of hours or days assuming there is not continued exposure to excessive noise If noise exposure continues the shift can become a noise induced permanent threshold shift which is a decrease in hearing sensitivity that is not expected to improve over time A standard threshold shift is a change in hearing thresholds of an average of 10 dB or more at 2 000 3 000 and 4 000 Hz in either ear when compared to a baseline audiogram Employers can conduct a follow up audiogram within 30 days to confirm whether the standard threshold shift is permanent Under 29 CFR1910 95 g 8 if workers experience standard threshold shifts employers are required to fit or refit the workers with hearing protectors train them in the use of the hearing protectors and require the workers to use them Recording criteria for cases involving occupational hearing
227. t fit the frequency response of the human ear when a sound dosimeter is set to A weighting it responds to the frequency components of sound much like your ear responds A weighting has the added advantage of being correlated with annoyance measures and is most responsive to the mid frequencies 500 Hz to 4 000 Hz B weighting B weighting is similar to A weighting but with less attenuation B weighting was an attempt to approximate human perception of loudness for moderately high sound pressure levels It is now outdated and no longer used C weighting A measurement scale that approximates the loudness of tones relative to a 90 dB sound pressure level 1 000 Hz reference tone C weighting has the added advantage of providing a relatively flat measurement scale that includes very low frequencies Criterion level The continuous equivalent 8 hour A weighted sound level as dBA that constitutes 100 of an allowable noise exposure dose in other words the permissible exposure limit For OSHA purposes this is 90 dB averaged over 8 hours on the A scale of a standard dosimeter set on slow response Dose Related to the criterion level a dose reading of 100 is the maximum allowable exposure to accumulated noise For OSHA 100 dose occurs for an average sound level of 90 dB over an 8 hour period or an equivalent exposure If a TWA reading is used rather than the average sound level the time period is no longer explicitly needed A TWA
228. taking separate measurements studies for different job tasks or processes within the same workshift The dosimeter can isolate the loudest job task the worker performs This data can be reviewed later by the CSHO to determine which job tasks contributed most to a worker s overall 8 hour TWA This feature is useful for assessing engineering controls The dosimeter microphone must be protected from wind and harsh materials Wind screens are optional indoors if air currents are minimal Always use a windscreen in areas with air motion outdoors and in dusty locations or during jobs when the microphone might get dirty Figure 23 The foam rubber wind screen will help protect the microphone Additional precautions are required to protect the microphone under the particularly harsh conditions that occur during abrasive blasting when the microphone should be clipped inside the abrasive blasting helmet Workers are understandably curious about the noise dosimeter and particularly the microphone Take time to explain that it only collects information on how loud the sounds are it does not record speech Activate the dosimeter and replace its screen cover or lock out the controls before the worker begins working As a good practice take sound level measurements frequently during the course of the noise dosimetry The sound level measurements document the noise in the area at specific points in time and from specific sources These values both validate the d
229. tances Critical Review of the Literature Ann Occup Hyg 41 4 455 65 CDC HHE 2011 Centers for Disease Control Health Hazard Evaluation Report Noise and Lead Exposures at an Outdoor Firing Range California HETA 2011 0069 3140 September Chang S J T S Shih T C Chou C J Chen H Y Chang and F C Sung 2003 Hearing Loss in Workers Exposed to Carbon Disulfide and Noise Environ Health Perspect 111 1620 24 Davis R R W J Murphy J E Snawder C A Striley D Henderson A Khan and E F Krieg 2002 Susceptibility to the Ototoxic Properties of Toluene Is Species Specific Hear Res 166 1 2 24 32 De Barba M C A L Jurkiewicz B S Zeigelboim L A De Oliveira and A P Bell 2005 Audiometric Findings in Petrochemical Workers Exposed to Noise and Chemical Agents Noise Health 7 29 7 11 European Agency for Safety and Health 2009 Combined Exposure to Noise and Ototoxic Substances Section III Chapter 5 Page 130 Fechter L D 1993 Effects of Acute Styrene and Simultaneous Noise Exposure on Auditory Function in the Guinea Pig Neurotoxicol Teratol 15 151 5 Hoet P and D Lison 2008 Ototoxicity of Toluene and Styrene State of Current Knowledge Crit Rev Toxicol 38 127 70 Johnson A C L Juntunen P Nyl n E Borg and G H glund 1988 Effect of Interaction Between Noise and Toluene on Auditory Function in the Rat Acta Otolaryngol 105 56 63 Johnson A C T C Morata A C L
230. tary positive displacement blowers e Rotary vacuum pumps and separators e Industrial fans e HVAC systems e Totally enclosed fan cooled electric motors e Gas turbines Pneumatic or Compressed Air Silencers In the earlier High Velocity Air Flow section it was mentioned that pneumatic or compressed air is a very common noise source in manufacturing plants Assuming sufficient noise reduction cannot be achieved by optimizing the air pressure setting the second step for controlling this class of noise source is to use commercially available silencers For retrofitting pneumatic devices selecting the appropriate silencer type is critical for this control measure to succeed over time If the source is a solenoid valve air cylinder air motor or some other device that simply exhausts compressed air to the atmosphere then a simple diffuser type silencer will suffice The disadvantage of these types of devices is that they can cause unacceptable back pressure Therefore when selecting a diffuser silencer it is important that the Section II Chapter 5 Page 37 pressure loss constraints for the particular application be satisfied All diffuser silencers can provide 15 to 30 dB of noise reduction For compressed air systems that perform a service or specific task such as ejecting parts or blowing off debris a number of devices are available for retrofit at the point of discharge Another typical application for compressed air is in blow o
231. tection simultaneously e g earplugs and ear muffs The noise exposure for workers wearing dual protection may be estimated by the following method Determine the hearing protector with the higher rated NRR NRRh and subtract 7 dB if using A weighted sound level data Add 5 dB to this field adjusted NRR to account for the use of the second hearing protector Subtract the remainder from the TWA It is important to note that using such double protection will add only 5 dB of attenuation For an example of a calculation of dual hearing protection see Appendix IV C Methods for Estimating HPD Attenuation of the OSHA Noise eTool For a more extensive discussion of how to use the NRR see the NIOSH website NIOSH has developed guidelines for calculating and using the NRR in various circumstances Method for Calculating and Using Noise Reduction Rating NRR Section III Chapter 5 Page 133 APPENDIX F Evaluating Noise Exposure of Workers Wearing Sound Generating Headsets F 1 Workers at Risk Workers can be overexposed to noise when they wear communications headsets as part of their work Clerical personnel aircraft pilots and other cockpit personnel air traffic controllers emergency personnel reservation clerks receptionists and telephone operators are just a few examples of the more than 3 million workers who can be exposed to high noise levels via communications headsets For a person wearing a sound generating headset the sound noi
232. terials add a rigid second layer adhered firmly over the viscoelastic layer This effectively increases the damping effect even with a very thin layer of the viscoelastic material The rigid second layer must be inelastic i e it must not stretch in any direction but it can be quite thin even a thin metal sheet or foil will work This combination of materials is popular because it reduces noise efficiently but takes up little space This concept is demonstrated in the previous figure in which two steel plates are separated by a layer of plastic foil Commercial vendors have developed numerous versions of these materials including metal tapes the tape provides the inelastic properties while the adhesive provides the viscoelastic layer Constrained layer laminates follow the same principle but laminate additional layers and thicknesses of rigid material metal or wood These laminates offer both good noise reduction properties and strength to the extent that some typically noisy mechanical parts e g covers for moving mechanical parts conveyer chutes can be made of the laminate The transmission loss of plywood and other composite materials is improved when a viscoelastic layer is sandwiched between layers One drawback is that special techniques are required to bend cut or weld these laminated materials When determining which damping materials to use one should consider the typical temperature and frequencies present in the equipment and
233. the sampled workers There are two shifts in this department The polishers are side by side and place the castings on wooden work tables The background noise when no one is using the pneumatic tools is 79 dBA You determine that retrofit mufflers barriers between adjacent polishers and absorptive treatment to the cement block wall in front of the polishing tables will result in a noise reduction of 9 dBA to 11 dBA at the worker s ear In this case the retrofit mufflers and sound absorbers and barriers are expendable and replaced every year Are these controls economically feasible given that the 8 hour TWA is less than 100 dBA a Determine the cost of the pneumatic mufflers i e small air exhaust muffler for a pneumatic hand tool From Table V 6 the unit cost of such a muffler is 16 00 average of high and low cost with no maintenance or production penalty involved In this case the retrofit mufflers and sound absorbers and barriers are expendable and replaced every year Therefore Section III Chapter 5 Page 96 16 00 x 5 grinders 80 b Determine the cost of the absorbers and barriers Five 4 x 4 foot areas of acoustical absorption are needed as well as three 8 x 8 foot barriers Two workers will require 1 5 days 12 hours to perform the installation There would be no production penalty and maintenance costs can be considered to be negligible Therefore 80 sq ft absorption x 6 480 192 sq ft barriers x 15 2 880
234. thereby reducing the worker s noise exposure iv Acoustical Enclosures Acoustical enclosures are the most popular path treatment used in industry Such an enclosure is composed of a dense outer casing often with a sound absorptive material on the interior surfaces to help dissipate the acoustical energy Enclosures can present difficulties for the production process Using them can involve many challenges such as interior heat buildup limited physical and visual access to the equipment difficulty getting the product in and out of the enclosure without sacrificing some noise reduction and maintenance personnel needing to disassemble the enclosure when repairing equipment It is not unusual for a reassembled enclosure to lose much of its effectiveness due to poor fittings and small gaps or openings in the enclosure Despite the challenges associated with enclosures they are often the most effective way to control noise hazards A well designed and relatively airtight enclosure can provide as much as 30 dB to 40 dB of noise reduction For example Figure 39 shows an enclosure with large retractable doors large observation windows internal lighting and ventilation among other features Driscoll Principles of Noise Control Figure 39 Large Equipment Enclosure with Retracting Doors Driscoll Principles of Noise Control Complete enclosures around noise sources are not always possible due to requirements to access mainte
235. tigation begins before you arrive on site First conduct a little research to determine whether noise hazards are likely If so plan to conduct noise measurements and monitoring Confirm that the instruments annual calibrations are current i e have not expired ensure that the batteries are fresh and calibrate the sound level meter and noise dosimeters before the opening conference This will permit you to begin obtaining sound level measurements during your initial walkaround at the site After these preparations you will also be ready to start obtaining personal noise dosimetry samples early in the visit while you have an opportunity to collect samples of significant duration The resulting noise dosimetry might not be full shift but it will provide valuable information regarding worker noise exposure that first day on site Sources of information about whether you are likely to encounter noise hazards at an establishment include e Previous inspection records for the establishment employer or other facilities in the same or similar industries e BLS information summarizing state or national data from the hearing loss column of employers OSHA 300 Logs e OSHA IMIS records on noise related citations from inspections conducted across the nation e NIOSH reports on the industry including Health Hazard Evaluations HHEs e Your own knowledge of or experience with the industry and its processes 1 Searching Online for Industry Noi
236. to be effective a receiver worker should be located in the direct field as opposed to the reverberant field A barrier s effectiveness in attenuating noise is maximized in a non reverberant environment Therefore if a receiver s noise exposure is predominantly from reverberation the effectiveness of the barrier will be limited The barrier should be placed as close as possible to the receiver or the noise source to minimize the angles from which sound is reflected to the receiver Section HI Chapter 5 Page 84 The dimensions of the barrier are also important In general the width of a barrier on either side of the noise source should be twice the height of the barrier Additionally any cracks or gaps in the barrier can significantly diminish the transmission loss value Any gap through which air can pass will allow a significant amount of noise to pass as well iii Reducing Reverberation A common way to reduce reverberation in a room is to install sound absorbing materials such as acoustic tiles in strategic places on the walls and ceiling surrounding the noise source Reverberation can be greater when the room surfaces are hard e g concrete cinder block corrugated metal in these environments sound absorbing materials can be beneficial This is a common treatment in theaters broadcast studios and sound recording booths Figure 38 shows a large open room in which sound absorbing baffles and acoustic tiles are hanging from the
237. turer s instructions on machine s and or processes contributing to high noise levels can help to establish knowledge and assist with determining potential engineering controls Explain to employer that you will arrange for a closing conference with him her to review your inspection findings H 5 Post Inspection Activities 1 There are several scenarios for how to enforce our noise standard Based on the specific inspection the CSHO needs to select the correct scenario that applies to that situation For example if noise exposures are gt 132 dose or an equivalent 8 hour TWA exposure of 92 dBA 90 dBA threshold and feasible engineering controls are cost effective then cite 1910 95 b 1 and conduct the following a Perform a cost comparison using your regional office s cost estimation for the average cost of a hearing conservation program As of 2011 the national average annual cost of a hearing conservation program is approximately 350 per worker b Research examples of technically feasible engineering controls for the specific machine and or process contributing to the noise levels Start with the equipment manufacturer c Start with easy solutions first d Once the engineering control has been determined contact noise control manufacturers to obtain prices for doing your cost comparison for determining economic feasibility engineering controls vs hearing conservation program Federal OSHA s Region III s Directive
238. ty for nighttime noise but is not used to evaluate compliance with OSHA standards as it is not an occupational issue Leq The true equivalent sound level measured over the run time Lrg is functionally the same as Lave except that it is only used when the exchange rate is set to 3 dB and the threshold is zero Section III Chapter 5 Page 114 Linear weighting A weighting most commonly found on upper model sound level meters typically used when performing octave band filtering analysis Max level The highest weighted sound level that occurred also allowing for the response time to which the meter is set If the meter is set for A weighting with slow response the max level is the highest A weighted sound that occurred when applying the slow response time Noise dosimeter A type of sound level meter that measures the dose of noise This instrument can calculate the daily noise dose based on a full workshift of measurements or a dose from a shorter sample The operator can select different noise dose criteria exchange rates and thresholds Octave bands Sounds that contain energy over a wide range of frequencies are divided into sections called bands each one octave A common standard division is in 10 octave bands identified by their center frequencies 31 5 63 250 500 1 000 2 000 and 4 000 Hz For each octave band the frequency of the lower band limit is one half the frequency of the upper band limit This is the most common
239. ulence in a Steam Pipeline Steam line Example A branch of a steam line has three valves which produce a loud shrieking sound The branch has two sharp bends which also pro duce a lot of noise Control measure A new branch is created with softer bends Tubing pieces are placed between the valves so that turbulence will be reduced or j eliminated before the stream reaches the next cutoff valve control valve valve ho k v m soft bend a y t H increased distance increased distance Driscoll Principles of Noise Control iii Mufflers and Silencers Mufflers also called silencers can be used on noisy pressurized air equipment to reduce noise at the source A muffler is a device that reduces the noise level from a moving air or gas stream such as one found in a pneumatic tool Figure 29 Like the muffler on an automobile it absorbs some noise before it can reach the receiver in this case the ears of the worker who is exposed to the noise Mufflers come in several configurations some more sensitive to dust and moisture than others In general mufflers must be cleaned on a regular basis to be effective at reducing noise if they are not cleaned they actually can increase noise levels Consult the muffler manufacturer for recommended cleaning procedures and frequency Figure 29 Schematic of Muffler Interior Section III Chapter 5 Page 73 iv
240. uman hearing into a manageable scale By definition O dB is set at the reference sound pressure 20 micropascals at 1 000 Hz as stated earlier At the upper end of human hearing noise causes pain which occurs at sound pressures of about 10 million times that of the threshold of hearing On the decibel scale the threshold of pain occurs at 140 dB This range of 0 dB to 140 dB is not the entire range of sound but is the range relevant to human hearing Figure 3 Section III Chapter 5 Page 10 Decibels are logarithmic values so it is not proper to add them by normal algebraic addition See Appendix B for information on the cumulative effects of multiple sound sources on the decibel level The decibel is a dimensionless unit however the concepts of distance and three dimensional space are important to understanding how noise spreads through an environment and how it can be controlled Sound fields and sound power are terms used in describing these concepts 6 Sound Fields Many noise control problems require a practical knowledge of the relationships between e A sound field a region in which sound is propagating and two related concepts e Sound pressure influenced by the energy in terms of pressure emitted from the sound source the distance from the sound source and the surrounding environment OTM Driscoll e Sound power sound energy emitted from a sound source and not influenced by the surrounding environment Soun
241. ustical Maintenance Program to maintain existing noise controls and keep machinery in good working order and 3 Go all the way with machine guarding to include the acoustical benefits pennies on the dollar Summary You have the tools to quantify the cost of a HCP prioritize noise control projects and to determine the return on investment toward eliminating the need for a HCP NIHL is 100 preventable I challenge you to be the key individual that makes a difference in the lives of workers at your location s Section III Chapter 5 Page 182 Dennis P Driscoll P E Associates In Acoustics Inc This period encompasses the entire IMIS record for noise through 2006 The data were first inspected and individual records with internal inconsistencies were removed One example of an inconsistency is a record coded as a personal noise result with units other than dB or percentage dose e g a value coded as a noise result with units inadvertently entered as mg m would have been removed before analysis The final dataset contained 224 339 personal noise exposure records Please note that workplace sampling is required and the historical data displayed should not be used to justify whether or not to monitor for overexposure to noise gt OSHA might also have conducted other inspections in that SIC that did not result in citations Inspections that did not include citations are not counted in this table To put t
242. vided with fit testing and donning methods in a controlled laboratory setting were not representative of the donning methods that workers used in the field EPA is considering options for updating this rule See Appendix E for current information on NRRs and hearing protection labeling requirements In special cases noise exposure originates from noise generating headsets See Appendix F for a discussion of the techniques used to evaluate the noise exposure levels of these workers 2 OSHA Noise Standards General Industry 29 CFR1910 95 Occupational Noise Exposure This standard is designed to protect general industry workers such as those working in the manufacturing utilities and service sectors The General Industry standard establishes permissible noise exposures requires the use of engineering and administrative controls and sets out the requirements of a hearing conservation program Paragraphs c through n of the General Industry standard do not apply Section III Chapter 5 Page 29 to the oil and gas well drilling and servicing operations however paragraphs a and b do apply The general industry noise standard contains two noise exposure limit tables Each table serves a different purpose e Table G 16 This table applies to the engineering and administrative controls section which provides a 90 dBA criterion for an 8 hour TWA PEL and is measured using a 90 dBA threshold i e noise below 90 dBA is not integrated
243. vides examples of some common noise control equipment and materials along with unit costs The cost for noise control equipment varies greatly including costs for different models of the same type of control If the actual cost is available for the control under consideration use the actual cost Otherwise in accord with the assumptions listed at the beginning of this section use the average cost in Table V 6 for cost estimating Percent Production Maintenance Cost Control Option dBA Reduction Cost in 2010 Penalty per Year J 5 E gq 5 3 oO 2 jab a Damping pad J 5 3 5 a o s ge 5 a io ji Nn ZIZ Elo ejg n O a poe Bs 5 oO i x o Q Ta k n w D 5 5 oO Pal o n 5 5 25 2 30 unit None None small i 5 2 300 unit None None average 2 lt r A gt large a z3 io H Dn oO oie 1g oO jr OQ a n oO 5 ga z3 j oO aS lt oO g lt gt large gt Nn N Nn 5 5 5 15 000 unit None 5 equipment i 5 20 5 000 35 000 unit None 5 workers 3 10 500 3 500 unit 0 20 5 partial r pr 3 10 4 000 35 000 unit 0 20 5 total Ceiling baffles Rated in Sabens 2 15 ft None NRC of 0 4 0 5 Note 1 Costs presented here were updated by contacting manufacturers for pricing over the period from May 2010 to April 2012 Note 2 Installation costs are not included According to data from the B
244. viduals but is typically in the micropascal Section III Chapter 5 Page 9 range The reference sound pressure is the standardized threshold of hearing and is defined as 20 micropascals 0 0002 microbars at 1 000 Hz The threshold of pain or the greatest sound pressure that can be perceived without pain is approximately 10 million times greater than the threshold of hearing It is therefore more convenient to use a relative e g logarithmic scale of sound pressure rather than an absolute scale OTM Driscoll 5 Decibels Noise is measured in units of sound pressure called decibels dB named after Alexander Graham Bell The decibel notation is implied any time a sound level or sound pressure level is mentioned Decibels are measured on a logarithmic scale a small change in the number of decibels indicates a huge change in the amount of noise and the potential damage to a person s hearing Figure 3 Decibel Scale Typical Sound Levels dBA 140 Threshold of Pain 130 Jet Taking Off 200 ft away 110 Night Club w music 100 Construction Site Boiler Room Freight Train 100 ft away 90 SA 70 om Chatter Clas 60 Conversation 3 ft away 50 Urban R ence 40 Soft Whisper 5 ft away 30 20 Silent Study Room 10 0 Threshold of Hearing 1000 Hz North Rim of Grand Canyon The decibel scale is convenient because it compresses sound pressures important to h
245. void corded earplugs as the cord would interfere with the muff seal Additionally hearing bands cannot be worn with earplugs or earmuffs as the connected band would interfere with the muff seal and there is no room to insert earplugs at the same time Figure 11 Earmuffs and Hearing Bands HPDs are rated to indicate the extent to which they reduce worker noise exposure New technologies are being developed to test the effectiveness of earplugs and could eventually change the way hearing protection is rated See Appendix E for current information on NRR methods ratings and requirements Section III Chapter 5 Page 45 HI Measurements A Equipment Several sound measuring instruments are available to CSHOs These include sound level meters noise dosimeters and octave band analyzers This section describes general equipment care followed by the uses and limitations of each kind of instrument 1 Noise Evaluation Instrument Care and Calibration Instruments that measure noise contain delicate electronics and require practical care Store and transport the equipment in its custom case Be aware of the instrument manufacturer s recommendations for proper storage for example some manufacturers recommend removing all batteries from stored equipment while others require a primary battery to remain in the instrument Make sure batteries will last the anticipated sampling period A battery tester can be useful CSHOs may need to instal
246. was revised to include Oregon OSHA specific equipment care and calibration In March 2014 information about agricultural worksites and maritime worksites was revised to make it specific to Oregon OSHA In March 2014 hyper links to related information were removed In June 2014 Oregon specific guidance on the use of presbycusis charts age correction factors was added to IV B 1 Reviewing Audiograms and Appendix J Reviewing Audiograms Section II Chapter 5 Page 2 SECTION III CHAPTER 5 NOISE TABLE OF CONTENTS I INTRODUCTION 5 95 sce oce teeter aaweer te i aai a ari 7 Il BACKGROUND INFORMATION 00 00 e eee 7 A What Is Noise 2c jccc20 n eresdbnadharaeheadhee beeadae 7 B Basic Qualities of Sound onanan nannaa 8 l Wayelength sesirioresrp i tno ee niria ea u Eka ew ode ea 8 2 PROQUENCYs2i4c bteedbeabadacavataeacheshagaes rakes 8 2 WPCC ys jase yee y ood eu ea aoe a sede ee aka 9 4 Sound PIOSSUTC 2 4 4 6 vice dodeaseecdeeiven deena sees 9 5e Decibels iss ichankeeaweta bee saeeeneaneea bee ed hans 10 O Sound Fields seers ce devennd sence seb PING reena 11 Te Sound POWS 653 sesia peer eaey secede see E eee 13 S Filtering s2i c428cccsberdhereeaeeearibaedcareeesacad 13 9 Octave Bands Frequency Bands 0005 14 10 Loudness and Weighting Networks 15 C How We Haf sods cate eeekeannra barika R EAR 16 D Hearing LOSS 6 0 ennes serei
247. y noise exposures in excess of 50 of the PEL Note If a citation will be issued the daily dose must be greater than or equal to 66 of the PEL 1 A large wood planer is situated in the middle of the production area A loader and off bearer operate the machine It has no noise controls The sound levels vary from 98 dBA to 118 dBA depending on the type of wood hard versus soft and the surface area of the wood being finished All production workers are exposed to the noise from the machine Administrative controls limit everybody s daily dose to less than 400 or 100 dBA Are engineering controls economically feasible a The equipment manufacturer contacted by phone indicates that one engineering option is to rebuild the drive mechanism and replace the cutters with those of a helical design According to the manufacturer s technical representative this will greatly improve the quality of the planed finish and reduce the noise level to about 90 dBA With the existing administrative controls everybody s daily exposure level would be reduced to less than 84 dBA A call to the regional service technician produced a cost figure of 10 000 per planer to retrofit with no maintenance or production penalty involved Per Assumption 7 the administrative controls contribute no additional cost The total cost is 10 000 for major modifications to one planer Per Assumption 1 this Section II Chapter 5 Page 98 engineering control has a life
248. zations e g Directive 2000 14 EC of the European Parliament and Council May 8 2000 Equipment manufacturers continue to add new information to this database in a standard format E Noise Control 1 Engineering Controls and Noise Control Programs Colgate Palmolive 2012 Excellence Award Corporate Wide Colgate Palmolive Company Colgate Palmolive won the 2012 Safe in Sound award through an extensive international effort to reduce noise exposure in its facilities around the world This online presentation outlines the company s efforts and successes and presents a summary of numerous adopted engineering modifications with photos notes on the changes made and examples of noise reductions achieved Section III Chapter 5 Page 108 National Aeronautics and Space Administration Approximate Sound Power Pressure Conversion Worksheet A simplified conversion method for sound pressure power conversion part of the NASA Buy Quiet Roadmap 2 Noise Control Products Sound and Vibration Magazine 2011 Buyer s Guide to Products for Sound and Vibration Control This guide is published annually Check here for the latest edition 3 Buy Quiet and Quiet by Design Programs National Aeronautics and Space Administration 2012 Buy Quiet Process Roadmap This is an online tool for navigating the procurement of low noise equipment Part of the NASA EARLAB Auditory Demonstration Laboratory website the Roadmap can be access

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