Sound Pressure Level (SPL) Meter - AV-iQ
Contents
1. MARS USER GUIDE ASM 2 Seven Range Sound Level Meter INTRODUCTION Congratulations on your purchase of the Nady ASM 2 sound level meter You ll find that it is an extremely versatile device for measuring sound intensity in just about any acoustic environment loud or soft high pitched low pitched or broad band intermittent or continuous You can use it to measure noise levels in factories schools offices and airports or to check acoustics of studios auditoriums and home theater installations Your meter features a large easy to read indicator for taking quick measurements anywhere Power is supplied by a 9 volt alkaline or NiMH battery so the meter is completely portable The meter s other features include e Seven sound level ranges allow measurements from 50 126 dB referenced to 0 0002ubar A and C weightings lets you check compliance with safety regulations as well as make acoustic analysis e Slow and fast response settings let you check peak and average noise levels e Built in battery condition indicator e Phono type output jack for connection to home theater or test equipment e The Threaded insert lets you attach the meter to a camera tripod for increased accuracy INSTALLING A BATTERY a gt CA The meter uses a 9 volt battery For the longest life and best performance we recommend an alkaline battery Open the battery compartment cover by pressing both sides at the lower striped portion and2. International For service please contact the Nady distributor in your country through the dealer from whom you purchased this product
3. the room s acoustics with your meter and a suitable test recording The test recording should produce pure tones one at a time at intervals spanning the audio spectrum Make a graph or table showing the sound levels generated by the individual tones This gives you a clear idea of the frequency response of your total system home theater equipment and room included The next step is to smooth out the reponse Adjusting tone controls and varying speaker placement might improve the sound significantly But to approximate the ideal flat response you could add a frequency equalizer to your home theater system Frequency analyzers such as the NADY GEQ Series graphic equalizers or the PEQ 5B parametric equalizer let you boost or cut response in different ranges as indicated by your frequency response analysis Properly equalized your system can sound like one costing considerably more Note If WEIGHTING is set to C the meter s frequency reponse is flat from 32 to 10 000 Hz 3 dB Above 10 kHz the frequency response of the meter drops off rapidly Besure to consider this when you use a test recording that includes tones at the extreme high end of the audio spectrum SPECIFICATION Range Battery One 9 volt rectangular type Switch Setting Range of Measurement Accuracy 2 dB 114 dB 60 dB 50 66 dB Standard 0 dB 0 0002 ubar oe T oa ve Weighting A and C 90 dB 80 96 dB Response Fast and Slow 100 dB 90 106 dB Signal Outp
4. etween you and the sound source as this might produce an error of several decibels in the frequency range above 100 Hz Position the meter so an imaginary line between you and the meter is perpendicular to a line between the meter and the sound source e Handle the meter carefully The microphone and meter movement are fragile and might be damaged if the instrument is dropped Do not operate the meter at a range setting that causes pegging of the needle This could damage the sound levels Follow these steps to select the desired response weighting and range 1 Set RESPONSE to FAST if the sound source you want to measure consists of short bursts or if you want to measure only peak values Or set RESPONSE to SLOW if you want to measure average sound levels 2 Set WEIGHTING to A if you want to measure noise level or C if you want to measure sound levels of musical material 3 Set RANGE to the highest setting 120 dB then adjust it downward until there is significant deflection of the needle v for the greatest accuracy always use the lower of any two possible settings For example if RANGE is set to 80 dB and the meter reads around 5 reset RANGE to 70 dB so the meter reads 3 for an actual sound level of 73 dB Important For meaningful readings any particular sound to be measured must be at least 10 dB louder than the background noise level While taking measurements minimize the effect of your body s presence When the sound is com
5. ing mainly from one direction the level reading might be significantly affected by reflections from your body For the most accurate readings and the best polar response point the meter s microphone toward the sound source when possible Sound Level dB Maximum Duration CHECKING NOISE LEVELS A Weighting SLOW Per Day hours This chart gathered from Federal state and local agencies shows standards for just how much noise is acceptable Noise is inevitable in almost any environment Depending on the level and duration noise can be a minor irritant a definite disturbance or even a threat to your hearing To use your meter to check noise levels set WEIGHTING to A and RESPONSE to SLOW Take 2 measurements at several points in the test area with the meter positioned properly 1 2 CHECKING ROOM ACOUSTICS ME Permissible noise exposures Extracted from U S Department of Labor Noise Regulations The size shape and furnishings of a room can have a tremendous effect on a home theater system s performance A hard room with bare surfaces tends to exaggerate treble response sometimes giving the music a strident quality A soft room with curtains over stuffed furniture carpet etc might reduce high frequency response so the bass sounds dominant giving you a mushy sound Dewaves might also develop in the room giving your system a peaky eccentric response The first step in solving this problem is to analyze
6. lifting the bottom Insert RADY a battery into the compartment as indicated by the polarity markings and marked inside AUDIO To test the battery set RANGE to BATT If the meter shows a reading in the red BATT TEST region the battery is still good Notes e Leave RANGE in the OFF position when the meter is not in use to conserve battery power e Remove the battery if you are not going to use the meter for a week or more ASM 2 RANGE Analog SPL Meter The RANGE selector lets you select one of seven sound level ranges each spanning 16 dB The numbers on RANGE refer to the center points of the seven ranges The needle indicator shows the actual sound level as a displacement from the center point For example if RANGE is set to 80 and the meter scale reads 3 the actual sound level is 77 as the value where RANGE is set the actual sound level is 80 dB 80 0 OUTPUT The phonotype OUTPUT jack lets you connect the meter to recording or other measurement equipment For example you might use an audio patch cord to connect the meter to the AUX or high level input of a recorder Note that the meter response will not be flat due to the A and C weighting networks Set Range so the maximum needle deflection is never greater than 4 to prevent the built in amplifier from clipping Use A weighting for voice recordings or C weighting for full range musical material The OUTPUT jack can also be connected to high impedance headphones or an oscillo
7. scope a frequency analyzer or other test equipment RESPONSE The RESPONSE selector has two settings FAST and SLOW In the FAST position the meter reacts quickly to changes in the sound level showing you the peak sound levels present in the enviroment In the SLOW position the meter is damped and indicates an average value sound level The effect of brief sound peaks is minimized in this position WEIGHTING Set WEIGHTING to weight the sound measurement for a particular frequency range When set to A the meter primarily measures frequencies in the 500 10 000 Hz range which is the area of greatest sensitivity to the human ear When set to C the meter measures uniformly over the frequency range from 32 10 000 Hz giving an indication of the overall sound level MICROPHONE The meter s built in microphone works best when you point it directly at a sound source TRIPOD ADAPTER You can mount the meter on a camera tripod standard 1 4 20 thread to eliminate hand noise and minimize the effects of sound reflected from your body This makes it easy to use the meter with auxiliary recording or test equipment CAL CALIBRATION Your meter has been accurately calibrated at the factory and normally will not require further adjustment If necessary an audio professional can use the CAL hole on the meter with special equipment including a sound generator to calibrate it MAKING MEASUREMENTS Important e Do not hold the meter directly b
8. ut 1 0 volt peak minimum into open circuit with full scale meter 110 dB 100 116 dB deflection at 1 kHz 120 dB 110 126 dB Battery Check Tests good from 7 0 To 10 5 volts Load Impedance 10 kohm minimum Expected Battery Life 110 working hours alkaline battery Distortion Less than 2 at 1 kHz 0 5 volt Size HWD 6 25 x 2 43 x 1 75 160 x 62 x 44 mm Microphone Electret condenser omnidirectional becoming slightly directional Weight 6 6 oz about 185 grams with increase in frequency Specifications are typical individual units might vary Specifications are subject to change and improvement without notice SERVICE U S Should your Nady ASM 2 Sound Level Meter require service please contact the Nady Service Department via telephone at 510 652 2411 or e mail to service nady com for a Return Authorization R A Number and a service quote if out of warranty Make sure the R A Number is clearly marked on the outside of the package and enclose a cashier s check or money order if not prepaid with a credit card Ship the unit prepaid to Nady Systems Inc Service Department 6701 Shellmound Street Emeryville CA 94608 Include a brief description of the problems you are experiencing The warranty card enclosed with this system contains additional valuable warranty and service information Keep it in a safe place for future possible reference Do not attempt to service this unit yourself as it will void the warranty
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