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AUDIOMETER AC50

1. 8 A 2 audj metr 6 audjometer T Fig 1 3 1 13 2 REAR PANEL AND ACCESSORIES Fig 1 3 2 20 Main fuse sockets holdingslow 5x20 0 25A fuses 21 Connection socket for additional protection 1 6 22 Mains and earth connection socket 23 Characteristics plaque 24 Socketfor earphonesoftechnician carryingout the test intercom 25 Patient s microphone connection socket intercom 26 Signal level adjustment control for intercom 27 Signal level adjustment control for speech audiometery input 28 Signal level adjustment control for auxilliary input for speech audiometry tests 29 Input socket for auxilliary signal in speech audio metery tests 30 Microphoneconnection socket for speech audio meterytestsor for theintercom operator s 31 Connection socket for patient sresponse button attachment 32 Connection socket for left Air Conduction AC earphones 33 Connection socketfor right Air Conduction AC earphones 34 Connection socket for Bone Conduction BC vibrator 35 Connection socket for amplifier correspondingto Free Field FF Speakers cannot be connected directly as apotency amplifier with graded levelsis needed 36 External printer connection socket 3n RS 232C socket for connection of audio meter to aPC or other computer system 1 7 38 Earphones for signal application by means of Air Conduction 39 Vibrat
2. 36925123 Name 2 Age Profession Right H Hz 1m123 258 505 IK 2k de Sk TUT c nn ga H Without With Masc L H 1 f r x fir Mean dB Hearing loss 3 48 46 Bilat h loss X 6 Type hear Fig 1 13 2 1 36 AUDIOMETRIC EXAM SIBELMED ACIO Date s NS 36925123 Name o Age 1 Profession Cn Success 102 T TET 1 5 165 5 16 15 20 25 36 35 40 45 50 55 65 75 85 98 95 1G CdE gt Fig 1 13 3 1 33 2 TECHNICAL SPECIFICATIONS As described in section 1 IN STRUCTIO N SFOR USEAND INSTALLATION the SIBELMED 5015 supplied in three different models which can be complemented by variousoptions not established as standard Forthisreasonthefollowingtechnical specifications correspondto an apparatus includingall possible options In each case the programming ofthe audio meter and parts not included should be taken into account 2 1 TYPES OF TEST TONALAUDIOMETRY Air conduction without masking Bone conduction without masking Air conduction with masking Bone conduction with masking Screening audiometry FOWLERTEST ABLB SISI TONE DECAY TEST LUSCHERTEST SPEECH AUDIOMETRY FREE AUDIOMETRY Multipl
3. 4 D isplay correspondingto right channel RED 5 Signal input level indicator for speech audiometry 6 Control keyscorrespondingto the left channel FT For selection ofsignal application route accordingto information panel 2 F2 For selection of mode or form of presentation ofthe signal accordingto information panel 2 F3 For selection of source or type of signal accordingto information panel 2 ar Attenuator or key used to increase level ofthe signal applied to patient in 5 dB decibel steps wg Attenuator or key used to diminish the level of signal applied to patient in 5 dB steps SIGN AL Silencer or when activated key which sends or blocksthe signal transmitted to patient depending on mode of direct inverted key 9 Key used to increase signal frequency of puretones applied to patient 125 250 500 750 1000 1500 2000 3000 4000 6000 8000 Hz 8 Key used to diminish the signal frequency of pure tones applied to patient 125 250 500 750 1000 1500 2000 3000 4000 6000 8000 Hz 1 4 9 INVER Key which enables the inversion of direct inverted functions ofthe SIG AL keys of each channel as well as other functions to be described further on 10 Control keys correspondingto the right channel F1 Selection of signal application route accordingto information panel 2 F2 Selection of mode or form of presentation ofthe signal accordingto
4. 4 Select the pure tone frequency form the following 1000 2000 4000 6000 and 8000 Hz 5 Apply 40 dB above the auditive threshold to the patient through the right hand channel and begin thetest Atthe end ofthe chapter Figs 1 13 2 and 1 13 3 show an audiometric file produced by a printer 1 11 PROCEDURE TO BE CARRIED OUT FORSPEECH AUDIOMETRY Speech or vocal audiometry basically consists of deter miningthe intelligibility threshold the patient hears and understandsthe word pronounced by means ofalist of words pronounced by alive voice or usingrecorded material either the procedure to be followed nor material to be used for this test are standardised and therefor are left at the specialist s discretion In this section only a basic description of how to use the apparatus in this mode will be given In the speech audiometry test only the CO NTIN UO USand ALTERNATELY PULSATING modes the SPEECH and VO CALNOISEVN functions and the AIR and FREE FIELD application channels are active Regarding general requirements the preparation and instruction ofthe patient are similar to those described in section 1 6 1 and B Particular care should be taken to ensure that the mechanics ofthe test in which words will be heard and must be repeated are understood by the patient W ith the audiometer prepared as desribed in section 1 4 INSTALLING AND TURNING ON THE AUDIO METER the function is selected in the following manner 1 Pr
5. 10 HL H earingLevel The test tone is applied to the patient by means of bone conduction vibrator WARNING THEBONECONDUCTION VIBRATORISA VERY FRAGILEITEMWHICH COULD BE DAMAGED BY SLIGHT KNOCKS IT IS THEREFOR RECOMMENDED THAT IT BE HANDLEDWITH CAUTION Theexamination consists of determiningthe auditive level when puretones without maskingare applied using bone conduction In order to do this the channel is selected as in the example below 1006 AC 1006 RIGHT LEFT Investigating thresholds usingbone conductionismuch more delicate to do andto interpret than other tests For thisreason special care must betaken when undergoingthese tests Correct positioningofthe vibrator is essential in determiningresults usingbone conduction It must be placed onthe mastoids andthe tone applied at some dB above the auditive threshold and the patient told to move the vibrator on his mastoids until findingthe point at which the tone is heard most loudly Ensure that the vibrator is firmly in contact with the mastoids and doesnot touch his outer ear in order to avoid conduction through the cartillage D uringthreshold examinations usingbone conduction without masking the opposite ear must be completely free that isto say without wearingair conduction earphonesor any other objects the occlusive effects of which could alter the results ofthe test therwise this should be indicated W ith the exception of the points mentioned above t
6. Level of increases 1 2 3 40r 5 dB Presentation in automatic mode Every 1 2 3 4 5 6 7 8 or 9 seconds Duration of increase 50 ms ascendingsignal 200 ms signal and 50 ms descending signal Precision 396 2 3 CONTROLLINGTHESIGNALLEVELS MAXIMUMSIGNALLEVELS Frequency 125 250 500 750 1000 1500 2000 3000 4000 6000 8000 AC dBHL 80 100 120 120 120 120 120 120 120 110 100 BC dBHL 50 60 60 70 70 10 70 10 Free field 70 80 80 80 80 80 80 80 80 MaskingAC dB HL 60 80 100 100 100 100 100 100 100 100 90 Masking BC dB HL 40 50 50 60 60 60 60 60 60 MaskingSN dB SPL100 Speech audiometry Air conduction dB HL100 Free field dB HL70 at 1 meter from the patient MINIMU MSIGNAL LEVELS 10 dB in all cases INCREASESIN SIGNAL LEVELS 5 dB steps 1 dB PRECISION OFSIGNALLEVELS Precision 3 dB TONE INTERRUPTION SILENCERS Independent for each channel Modes direct signal when buttonis pressed inverted signal when button not pressed Attenuation gt 80 dB Ascension and descensiontime 50 ms 2 4 OTHERFUNCTIONS PERSONALISED PROGRAMMING OF FUNCTIONS PRESENTATION OFSTATEOFFUNCTIONS Independent for each channel 16 character alphanumerical LC D display INTERCOM Between operator and patient Signal level controller MEMORY RAM apacity 50 tests OUTPUTS C entronicsParallel type printer RS232C series port 2 5 TRANSDUCERS AIRCONDUCTION TDH39 earphones pair BONECONDUCTION B71 or B72 vibrator
7. and sent to a final amplifier where sufficient power is reached to feed the monitor s earphones 3 6 FREE FIELD O ptional Free Field audiometry requires an apparatus which works in the place of the patient s earphones The signals proceeding from the audiometer are applied througha connections to the inputs of a set of two potency amplifiers which power two loudspeakers situated at a certain distance from the patient The gauging of free field is done at a distance of 1 meter from the loudspeaker at the center of the axis upon which the patient is sitting the patient s ear and the center ofthe loudspeaker being situated on the same horizontal plane The amplifiers are powered directly from the mains and have no controls or indicators except for the ON OFF switch and corresponding indicator light 34 IINNZH L3NINSZH LHDIJ LNO 29 915 W JAALNI 3 5 UENOILd603 H31NIBHd AWTdSIO 31NINdJ NIUM A 7dahns 5432111894915 qo 21507 423 MOLINGH 2NO0H3I93H CTWNOTLdO gt M OMSINI Y314171dH0 33d 3NOHdOH2IM 1 31194 HOLIMS TOS LNOD TOY INOD HOD331NI 4055300 1543 35 3SION 311HM 54321118915 20719NB HWO2331
8. EARPHONES 520 550 001 1 BONECONDUCTION VIBRATOR Dependingon model 520 641 010 50 AC50AUDIO METRY GRAPH 305 350 020 1 MAINSCONNECTION CABLE2m 520 600 MUI 1 SIBELMED AC50USER SMANUAL 175 600 020 1 RED BALL PO INT PEN 175 600 060 1 BLUEBALL POINT PEN 520 670 004 1 SPEECH AUDIO METRY MICRO PHONE Dependingon model 520 680 003 1 PATIENT SIN TERCO M MICRO PHONE D ependingon model 520 680 002 1 SET O FEARPHO NESFO R MONITOR Dependingon model The optional parts will be supplied alongwith the accessories necessary to enable each correspondingtest These code numbers may be used in order to order replacements of accessories 1 2 NOTICE Incompliancewith variousregulations it isrecommendedthat the electromedical apparatus be checked periodically in order to ensurethat it isfunctioning correctly and for the safety ofthe patient user and working environment Besidesthe necessary routine checks on the SIBELMED AC 50 audiometer it is advisable gaugethetransducersandto servicethe safety systems adjustments functionsetc at least everytwelvemonths ISO 8253 1 T hismust also bedone whenever it issuspected that the machineisfunctioningincorrectly Theseservicesmust becarriedout inline withthe manufacturer s SIBEL S A C heckingand Adjustment Procedures bythe manufacturer itselfor by technical personnel qualified and authorised by SIBEL S A RESPONSIBILITY OF MANUFACTURER SIBEL S A will hold itself responsiblefor the safety reliability a
9. LLINTRODUCTION The SIBELMED AC 50clinical audio meter isacompact apparatus with two channels based principally on a tone generator anoise generator aset of air conduction earphones abone vibrator and two alphanumeric liquid cristal display screens T he whole system is controlled by amicro processor which enables audiometric examinationsto be carried out reliably quickly and simply in order to determine hearingthresholds and perform screening tests as well as supraliminar tonal tests The SIBELMED AC50 clinical audiometer was developed entirely in Spain in keeping with the latest technology after morethan 15 yearsofexperience inthefield designingand manufacturingsimilar apparatus The apparatus functional design combined with the minimisingofelectromechanical components allow for the production of apparatus which provide alasting service carryingo ut audio metric tests TheSIBELMED AC 50 clinical audiometer was designed in collaboration with prestigious experts in the field and meets the standard criteriaofthe ational Institutions U N E aswell asthe International Institutions I E C 1 5 0 etc L2 PREVIOUSOBSERVATIONS This audio meter is manufactured using professional components in perfect condition under strict quality control tests However accidents may occur duringtransport or storage so it is advisable to check the apparatus and complementary accessories over before installation WARNING IF ANY DAMAGE IN THE PACKAGING
10. mm format DIN A4 279 mm format B Testswhich can be printed The information which can be printed includes that of all the tests defined in section 1 5 AUDIO METRIC TESTS with the exception of FREEAUDIO METRY TONALAUDIO METRY FOW LER TEST SISI TONEDECAY TEST L SCHER TEST SPEECH AUDIO METRY C Procedureto be followed for teststo be printed The procedure to be followed whilst performingtests which are to be printed are as follows 1 Presskey 11 to assignareference number ofamaximum often charatersto the patient to be subjected to the test This reference is introduced by means of the keys for digits 0 to 9 and finalised by means oftheINTRO 19 key 2 Select the option which corresponds to the teest to be carried out by means ofthe Menu key 12 Thetest beingcarried out and the patient s reference number can be seen at all times If no reference number has been assigned the information cannot be recorded 3 Performthetest asdescribed in section 1 6 PRO CEDURETO BECARRIED OUTFORTONAL AUDIO METRY andthefollowingtests T hefollowingconsiderations must be taken into account for each correspondingtest TONALAUDIOMETRY The only variation is that once the threshold has been determined with the channel level correspondingto that threshold the IN TRO key 19 is pressed for and for afew secondsthe right channel display will show the message TH RESH O LD STO RED Ifmaskingisbeingapplied to the opposite ear the le
11. noise level is low enough not to distort test results Failing this NOISE SUPPRESSORS can be adopted for the earphones OPTIONAL Caution must be taken not to place the apparatus anywhere near water or other liquids which may splash it or to place other objectson apparatus which could impede the circulation ofair inthe machine while itis functioning The sequence of operations needed to prepare the SIBELMED AC50 to carry out audiometric tests is as follows 1 Main switch 1 in position 0 O FF light off 2 Connectthe mains connection cable to socket 22 and to the mains 220V 50 60 Hz 10 XXXX 3 Connectthe accessoriesto the correspondingsockets W hen all the steps described have been gone through the apparatus will be ready to operate 1 4 2 TURNING THE AUDIO METERON In order to turn the audiometer on press switch 1 to position I O N The switch will then light up For some seconds the apparatus will carry out an auto check soasto verify whether all the accessories are connected and that the original gaugingis correct Ifthe result is negative the machine will indicate this T his gauging check presupposes that both the air conduction and bone conduction transducers are working correctly and have not deteriorated In order to preventthis and also when improper functioningis suspected 1 9 itisnecessaryto run an MIN IMUM PERIOD ANNUALGAUGIN G with an artificial ear and mastoids O nce the auto check is completed the audio m
12. patient issitting hisear andthe center ofthe speaker beingonthe same horizontal plane 1 13 PRINTOUT AND MEMORIZATION OFAUDIOMETRYTESTS The SIBELMED AC50 audiometer has the capacity to print and or memorize some of the possible audiometrictests within the apparatus itself or in an external database In order to understand more clearly Fig 1 13 1 shows block diagram in which the flux followed by the audiometric data generated bythe apparatus is shown DETECTIO N OFTHRESHO LDSTEMPO RARY MEMORY PRIN TER INTERN ALDATABASE PC DATABASE TRANSITO RY MEMO RY THRESHOLD DETECTION PRINT INTERNAL DATA BASE PC DATA BASE Fig 1 13 1 Asshown in the diagram the audio meter has the capacity to store the auditive thresholds detected in a temporary memory in order to perform the followingtasks Audiometric data printout through an external printer Storing ofaudiometric datainanINTERNAL DATABASE Transferring of audiometric datato an EXTERNAL DATA BASE IN A PC 1 13 L PRINTOUT OFAUDIOMETRIC DATA A Typeof printer The printer to be connected to socket 36 must be an Graphics type printer AnH PD esk jet 520 ink jet printer or compatible alternative for adaptabilityto the apparatus and low noise level is recommended The presentation format can be selected by means ofthe O PTIO SMEN U key 12 Two format types are availablefor selection by enteringREPO RT FO RMAT 11 inch 279 4
13. 5 Select another frequency and repeat number 4 6 0 nce the right ear has been tested repeat the process desribed in numbers 4 and 5 blockingthe signal the right channel and activating that of the left channel as seen below dB F1F2 F3 SISI dB F1F2 F3 lime 48 AC 1860 RIGHT LEFT The dB level here is given as a guide 1 7 PROCEDURETO BECARRIED OUT FORFOWLERTEST Thistest is also called Alternate Binural Loudness Balance or It is applied in order to determine whether there is recruitment when the threshold of one ear is normal or inferior to 30 dB and the other showsa loss of between 25 and 60 dB Therequirements regarding general aspects preparation and instruction ofthe subject are similar to those described in section 1 6 1 A and B W iththe audiometer prepared asdesribed in section 1 4 IN STALLING AN D TURNING THEAUDIO METER O proceed asfollows Typekey12ontheO PTIO NSMENU Usingkeys 7 and 8 select the FO W LER TEST option and enter by means ofthe IN TRO 19 key The procedure to be followed for this test consists of applying a tone of equal frequency to both ears alternating between them once asecond The level of intensity for the best ear is progressively increased starting at the threshold in 10 to 30 dB steps while the subjective sonority ofthe poorer ear is equalised and its correspondance with the better ear will be shown on agraph In this test the signal modes CO NTIN UO USand ALTERN
14. AINTENANCE TheSIBELMED AC 50 audio meter requires general and preventive maintenance as do any machines and particularly those with medical applications with the primary object beingthe safety ofthe patient operator and the environment and secondlyto guarantee the reliability and precision ofthe functions for which it was made This entails aseries of routines which must be gone through 5 1 GENERAL MAINTENANCE The general maintenance is necessary in order to keep the apparatus functioningcorrectly The personwho carries out this operation needs no special technical knowlege except familiarity with the functions and handlingofthe machine user ofthe apparatus should normally do the job himself The tasks to be carried out areas follows 5 LI CLEANINGTHEAUDIOMETER W ipethe audio meter gently with cloth slightly dampened in water then wipe the apparatus dry Special care must be taken that no liquid enters the machine or its sockets Do not use abhrasive substances or solvents 5 1 2 CLEANING THE ACCESSORIES Thesame method as that described for the apparatus itself should be used for the accessories The cushions of the air conduction earphones may be removed and washed more thoroughly in soap and water before beingdried completely with acloth and then replaced onthe earphones WARNING The bone conduction vibrator is a very fragile element which could be damaged by any slight knocks it is therefor recommended that it be handl
15. ATELY PULSATING the PURE TON Esignal sourceandtheAlR application channel are activated 1 8 PROCEDURETO BECARRIED OUT FORSISITEST The SISI test Short Increment Sensitivity Index consists of measuringthe ear s capacity to perceive short increases in intensity The test consists of applying 1 dB continuo ustone increases atan increase rate of 50 ms lasting200 ms and descending to 50 ms The level of increase can be from 2 to 5 dB to train the poatient The application of the increase can be automatic or manual and the interval in auto matic mode can vary between 1 and 9 seconds the normal value being5 seconds The apparatus incorporates a counter for the number ofincreases applied ifthey are at 1 dB The maximum number is 20 increases Therequirements regardinggeneral aspects the preparation and instruction of patients are similar to those described section 1 6 1 A and B Special care should be taken to explain to the patient the mechanics of the test in which aconstant pure tone will be heard at times and ajump in the intensity ofthe tone at others Atthis moment he should respond by pushingthe response button W ith the audiometer prepared as described in section 1 4 INSTALLING AND TURNING ON THE AUDIO METER the function may be selected follows 1 Presskey 12 onthe O PTIO N SM EN U By meansofkeys 7 and 8theoption SISI is selected and the test entered using the IN TRO 19 key 2 The displays will appear asin th
16. CLINICAL AUDIOMETER SIBELMED AC50 520 600 MU 2 USER S MANUAL SIBELMED AC5OCLINICAL AUDIO METER USER S MANUAL EO1 CONTENTS LINSTRUCTIONSFORUSE AND INSTALLATION 1 1 INTRODUCTION 1 2 PREVIOUS OBSERVATIONS 1 3 DISTRIBUTION OF CONTROLS INDICATORSAND CONNECTIONS 1 3 1 FRONT AND SIDE PANEL 1 3 2 REAR PAN EL 1 4 INSTALLING AND TURNING ON THE AUDIOMETER 1 4 1 IN STALLING TH AUDIO METER 1 4 2 TURN ING THEAUDIO METERON 1 4 3 DESCRIPTIO N OF DISPLAYS 1 4 4 PRO GRAMMIN G THEAUDIO METER 1 5 AUDIOMETRIC TESTS 1 5 1 TON ALAUDIO METRY 1 5 2 FO W LER TEST 1 5 3 SISI 1 5 4 TON EDECAY TEST 1 5 5 LUSCHER TEST 1 5 6 SPEECH AUDIO METRY 1 5 7 FREEAUDIO METRY 1 6 PROCEDURE TO BECARRIED OUT FORTONAL AUDIOMETERY 1 6 1 DETERMIN ING AUDITIVETHRESHO BY AIR CONDUCTION WITHOUT MASKIN G 1 6 2 DETERMINING AUDITIVETHRESHO LD BY AIR CONDUCTION WITH MASKING 1 6 3 DETERMIN IN G AUDITIVETHRESHOLD BY BONECONDUCTION WITHOUT MASKIN G 1 6 4 DETERMINING AUDITIVETHRESHOLD BY BONECONDUCTION WITH MASKIN G 1 6 5 SCREEN ING AUDIO METRY 1 7 PROCEDURE TO BE CARRIED OUT FORFOWLERTEST 1 8 PROCEDURE TO BE CARRIED OUT FOR 5151 TEST 1 9 PROCEDURE TO BE CARRIED OUT FORTONE DECAY TEST 1 10 PROCEDURE TO BE CARRIED OUT FORTONE DECAY TEST 1 11 PROCEDURE TO BE CARRIED OUT FOR SPEECH AUDIOMETRY TEST 1 12 PROCEDURE TO BE CARRIED OUT FOR FREE AUDIOMETRY 1 13 PRINTOUT AND MEMORISATION OF AUDIOMETRY TESTS 1 13 1 PRINTOUT OFAUDIO METRIC DATA 1 13 2 MEMO R
17. DUCTION WITH MASKING SCREEN ING AUDIO METRY Asdescribed previously the mechanics needed to carry out certain audiometric examinations described inthis manual T hese methods are not the only ones and therefor must be adapted to the specialist s criteria in each case Followingis adesription of each type tonal audiometry accordingto regulation ISO 8253 1 1 6 1 DETERMINING OF AUDITIVE THRESHOLD BY AIRCONDUCTION WITHOUT MASKING The SIBELMED AC 50 incorporates the followingpure tone frequency levels to be applied by air conduction Hz 125 250 500 750 1000 1500 2000 3000 4000 6000 8000 Max dBHL 80 100 120 120 120 120 120 120 120 110 100 Min dBHL 10 10 10 10 10 10 10 10 10 10 10 HL HearingLevel A GENERALASPECTS Technicians Before performingthe audiometric tests technicians must be instructed in the theory and practice of thesetests asit will be necessaryto take decisions such as W hich ear should be examined first ormally that considered to have the best hearing by the patient smasking required or not W hen doesthe patient sresponse correspond to the signal T he AC 50 indicates discrepancies sthereany external noise or patient s response which could invalidate the test W illthetest be continued or reapeated duringthe interruptions etc TestingTime Itisimportantto try not to tire the patient asthe results may be difficult to obtain ifthe test exceeds 20 minutes without pausingt
18. FREE FIELD Loudspeakers and amplifier SPEECH AUDIOMETRY MICROPHONE D ynamictype 2 6 REGULATIONSAPPLICABLE ELECTRICALSAFETY 601 1 UNE 20 613 AUDIOMETRY 645 UNE 20 641 150 8253 1 CALIBRATION Air conduction ISO 389 UN E 74 020 Boneconduction ISO 7566 2 7 GENERALINFORMATION FUNCION CONTROL Microprocessor Access T ouch type keyboard Presentation LC D display ATMOSPHERIC CONDITIONS Storagetemperature 0to 60 C W orkingtemperature 10to 40 Relative humidity 9096 without condensation POWERSUPPLY 220 V 50 60 Hz 10 other voltages optional POWER 20 VA DIMENSIONS idth 470 mm Depth 250 mm Height 95 mm WEIGHT A4 5Kg 3 FUNCTIONING PRINCIPALS In order to make evaluations of physiological capacity by means of electronic aparatus it is necessary to reproduce physical conditions capable of stimulating and producing the physiological responses to be evaluated Regarding the SIBELM ED AC 50 audiometer its function is to reproduce defined sounds which when applied at graded standard levels permit responses adequate to the capacity of the receiver to be obtained The electronic circuits incorporated into the audiometer in order to achieve this end are described below To provide a clearer understanding block diagrams 3 1 and 3 2 are included 3 1 SIGNAL SOURCES 3 1 1 TONE GENERATOR The Tone Generator consists of a W ein Bridge oscillator the frequency of which can be selected f
19. IS FOUND CONTACT THE TRANSPORT AGENCY AND DISTRIBUTORIMMEDIAT ELY BEFORE PROCEEDINGTO INSTALLTHE APPARATUS DO NOT DISPOSE OF PACKING BAGS ETC UNTIL THE CORRECT FUNCTIONING OF THE APPARATUSHASBEEN THOROUGHLY CHECKED The SIBELMED AC 50 series of audiometersis presented in three different models SIBELMED AC50 B SIBELMED AC50 C SIBELMED AC50 D Thefollowingtable showsthe basic characteristics comprising each standard model X plus the parts which can be included optionally O At any stage if desired a given model may be converted into asuperior one by adding the corresponding parts To do this it will be necessary to contact SIBEL S A s commercial departmentor distributor 1 1 MODELS AC50 B AC50 C AC50 D TVVOCHANNELS X X X AIRCONDUCTION X X X BONECONDUCTION o X X FREE FIELD o o o SPEECH AUDIOMETRY o X NARROVV BAND NOISE X X X SPEECH NOISE X X PULSETONE X X X FREQUENCY MODULATION X X X AMPLITUDE MODULATION X X ABLB X X X SISI o X AUDITIVELOSSCALCULATION X X X INTERCOM o o AUTOTESTING X X X PATIENT SRESPONSEBUTTON ATTACHMENT X X X OUTPUT TO PRINTER X X X RS232 C CHANNEL X X X INTERNAL MEMORY X X X PC DATABASE o o o AUDIOCUPSAC o o o PRINTER o o o CARRYING BAG o o o TheSIBELMED AC 50 audiometer consists ofthe followingitems and accessories CODE QUANTITY DESCRIPTION 520 600 000 1 SIBELMED AC50 AUDIO METER Dependingon model 520 540 001 1 PATIEN T SRESPO N SEBUTTON ATTACHMENT 520 540 002 1 SETOFAIR CONDUCTION
20. ISATION OFAUDIO METER RESULTSIN THE INTERNAL DATABASE 1 13 3 EXTERN AL DATABASE AN D RS 232 CHANNEL 1 14 AUTOMATIC CALCULATION OF AUDITIVELOSS 1 14 1 PERCEN TAGEO FAUDITIVELO SS 1 14 2 PERC EN TAG E O F BILATERAL AUDITIVELO SS 1 14 3 MEAN AUDITIVELOSSIN dB 1 14 4 CATEGORIZIN OFAUDITIVELO SS 2 TECHNICAL SPECIFICATIONS 2 1 TYPESOF TEST 2 2 SIGNAL GENERATORS 2 3 CONTROLLING THESIGNAL LEVELS 2 4 D0T HER FUNCTIONS 2 5 TRANSDUCERS 2 6 REGULATIONSAPPLICABLE 2 7 GEN ERAL INFORMATION 3 FUNCTIONING PRINCIPALS 3 1 SIGNAL SOURCES 3 1 1 TO N EGEN ERATOR 3 1 2 SPEECH AUDIO METRY 3 1 3 NARROW BAND NOISE 3 1 4 VOCAL NOISE 3 1 5 S0 URC E SELECTO R 3 2 RIGHT HAND CHANNEL 3 2 1 DULATOR 3 2 2 ATTENUATOR 3 2 3 INTERRUPTING THESIGNAL SILEN CER 3 2 4 CHANNEL SELECTOR 3 2 5 AMPLIFIER 3 3 LEFT HAND CHANNEL 3 4 MCROPROCESSOR 3 4 1 PHYSICAL D ESCRIPTIO N 3 42 PROGRAM 3 4 3 RAM MEMORY 3 44 CPU 3 4 5 PERIPHERALS 3 5 INTERCOM 3 6 FREE FIELD 4 AUDIOMETRY TECHNIQUE 5 GENERAL MAINTENANCE PREVENTIVE MAINTENANCE CORRECTIVE MAINTENANCE 5 LGENERAL MAINTENANCE 5 1 1 CLEANING THEAUDIO METER 5 1 2 CLEANING THEACCESSO RIES 5 2 PREVENTIVE MAINTENANCE 5 2 1 AND SUBJECTIVETESTS 5 2 2 OBJECTIVE CHECKING 5 3 CORRECTIVE MAINTENANCE 6 MODIFICATIONS R Date March 1995 Approved Date March 1995 SIBEL S A Dos de Maig 290 08025 BARCELONA 1 INSTRUCTIONSFORUSE AND INSTALLATION
21. NI NOLINS NTNMG M INSILUd CTONOTIdO gt LINN 07313 3384 934955 31413448 33 1331 eta 9 011402 NOTISMAIN S ANCE NOILDNGNOD IU 1437 H3IJINdHH NOL LONANOD IU 97314 3343 1337 3343 1H9I3S SI N ar q 3510 1723 5594 HOLUDN311U0 1331 449 NOTLIDANA us pee tl 333243115 H5I3Y M L N3L M iH5IM NOTIONS AH9 IM 4510 1ndou LH9 IM 3009 100H NOIUHZN3D ANO 1 1 CUNOLldo Ad quoTanu AIAT H233JS 3 6 4 AUDIOMETRY TECHNIQUE Audio metry technique is very extensive asaresult ofthe large number of variationsin existence A description of each of these variations would be a complex undertakingand is not the object of this manual Because ofthis specialists who are interested in complementary information should refer to any ofthe many books published onthe subject 5 GENERAL MAINTENANCE PREVENTIVE MAINTENANCE AND CORRECTIVE M
22. PEECH AUDIOMETRY Speech or vocal audiometry basically consists of deter miningthe intelligibility threshold the patient hears and understandsthe word pronounced by means ofalist of words pronounced or recorded material There are many variations of speech audiometry which are not described in this manual and remain at the discretion ofthe user The test may be done using model AC 50 D and also with model AC 50 C ifthe option isincorporated 1 5 7 FREE AUDIO METRY Thisoption included in the audiometers MU ST NOT BECONFUSED WITH FREEFIELD Byselecting FREE AU DIO METRY the user can carry out any other test usingthe audio meter including those described above asthe audio meter permitsaccessto and selection ofall functions although some may beirrelevant Inthe tests described previously the machine ssoftware blocks some functions which would not normally be used for that particular test and variations are therefor impossible U singthe FREEAUDIO METRY option permits accessto any ofthe functions possible for the apparatus These tests can be done usingmodels AC 50 B AC50 C and AC50 D 1 6 PROCEDURETO BE CARRIED OUT FORTONAL AUDIOMETRY Variationsintonal audiometry methods are as follows DETERMINING OFAUDITIVETHRESHOLD BY AIRCONDUCTION WITHOUT MASKING DETERMINING OFAUDITIVETHRESHOLD BY BONECONDUCTION WITHOUT MASKING DETERMINING OFAUDITIVETHRESHOLD BY AIRCONDUCTION WITH MASKING DETERMINING OFAUDITIVETHRESHOLD BY BONECON
23. T he inverted position is used to stop the signal to the patient when the key is pressed O therwise there is asignal Move from one option to the other by pressing the SIGN AL key ofthe correspondingchannel and briefly pressingthe IN VER key W hen the digits EF appear on the screen it indicates that there is a signal being applied to the patient or if not that there is none D DETERMINING THRESHOLDS O nce the steps previously described have been followed the auditive thresholds of each ear must be determined NOTICE IN ORDERTO MEMORIZE THE THRESHOLDSSO ASTO PRODUCEA GRAPH THROUGH APRINTER ORTO MEMORIZETHEMIN THEINTERNAL DATABASE AND ORTRANSFER THEMTO A PC DATABASE SEE SECTION 1 13 PRINTOUT AND MEMORIZING OF AUDIOMETRIC TESTS Thetesttone iscontinuousand lasts between one and two seconds T hesignal will be applied in direct mode when pressingthe SIGN AL key W hen the patient responds the interval between tones will vary but will not be shorter than the duration of the tone NOTE Thepatient sresponse on pressingthe response button will be shown flashingon the display indB ofthesignalapplied Ifthe patient pressesthe response button when no signal hasbeen applied the displays briefly indicatethe figures dB F1F2 F3 SISI dB F1F2 F3 WIHTOUT SIGNAL WIHTOUT SIGNAL RIGHT LEFT Inthe first place it will be useful to carryout a practice test in order to familiarise the patient with the process Do th
24. ainingthe SIG N AL kay pressed and typingthe IN VER key and releasingboth so that the audio meter works in inverted mode there will bea continuous signal unlessthe SIG N AL key is pressed 9 Thestimulus counter right channel display will accumulate 1 dB increases which are applied and the reply counter right display channel will indicatethe responses received T hese counterscan bereset to zero at anytime usingthe RESET key 15 10 0 ncethe selected increases have been sent they are recorded as arethe responsesreceived and the frequency is changed Theresultsare normally recorded in percentage form in accordance with number of replies x 100 number of increases 11 0 ncethe frequencies have been examined in the reight ear the test is repeated inthe left ear Atthe end ofthe chapter Figs 1 13 2 and 1 13 3 show an audio metric file produced by aprinter 1 9 PROCEDURETO BECARRIED OUT FORTONEDECAYTEST TheToneDecayTestaccordingto Carhart consists ofapplyingatone 5 dB abovethe threshold to the patient and observingwhether it is perceived clearly over 60 seconds N ormally itis perceived duringthistime If itis not the level is increased in 5 dB steps until heard and further until the patient confirms that he can hear it for the entire minute Regarding general requirements the preparation and instruction ofthe patient are similar to those described in section 1 6 1 and B Particular care should be taken to ensure that the me
25. cal analogical selectors which are controlled by the processor O ne of them directs the signal of one of the four sources to the right channel and the other directs them to the left channel 3 2 RIGHT CHANNEL The right channel consists ofthe set of circuits the function of which is to treat the signal received from the source and direct it to the right air conduction earphone to the bone conduction vibrator or to the right free field output 3 2 1 MODULATOR The first stage of the channel consists of a circuit capable of applying an amplitude modulation which is variable in depth and time dependingon the code received by the processor to the signal which can proceed from any source 3 2 2 ATTENUATOR The attenuator is made up of various stages formed of resistors mounted as dividers gauged in dB from whichthe analogical selectorsread the levels accordingto combinations defined by codesreceived from the processor 3 2 3 INTERRUPTING THE SIGNAL SILENCER The connection and disconnection of the signal is done by means of a circuit formed by an operational amplifier mounted as an invertor and two FET transistors The order received from the processor is conformed by means of an integrator in order to activate or disactivate the silencer progressively and gradually in accord with regulations 3 2 4 CHANNEL SELECTOR Ananalogical selector directs the signal either to the right air conduction amplifier the bone conduction 3 2 amplifi
26. chanics ofthe test in which aconstant pure tone will beheard are explained to the patient The response button must remain pressed while the patient is listening W ith the audiometer prepared as desribed in section 1 4 INSTALLING AND TURNING ON THE AUDIO METER the function is selected in the following manner 1 Press 12 onthe O PTIO N SMENU Usingkeys 7 8the TO ED ECAY TEST option is selected Enter the test by means of the INTRO key 19 2 The displays will appear similar to the ones below 68 AC 1002 AC 1882 RIGHT LEFT Thetwo charactersonthe right ofthe left channel will work asatimer countingup to 90 seconds The timer starts when the signal is applied 3 Select asignal level to apply at 5 dB above the auditive threshold level at oneofthefollowingfrequencies 250 500 1000 2000 and 4000 Hz 4 Begin the test by applyingatone by means ofthe SIGN AL key in either direct or inverted mode for 60 secondsifthe response continues O therwise increase the tone level Atthe end ofthe chapter Figs 1 13 2 and 1 13 3 show an audiometric file produced by aprinter 1 10 PROCEDURE TO BE CARRIED OUT FORL SCHERTEST The L scher test consists ofapplyingatonelevel 40 dB above the auditive threshold modulatingthe amplitude and determiningthethreshold from the modulation T his will be found by raisingor loweringthe level where the subject can no longer hear the wavering oftheton
27. ck consists ofa general technical testingofthe security systems adjustments functions gaugings etc which are programmed into the apparatus The gaugingis carried out with the aid of an artificial ear and mastoids in accordance with the applicable regulations THESE CHECKS SHOULD BE CARRIED OUT AT LEAST ONCE A YEAR in accordance with the Procedure for C heckingand A djustingthe SIBELM ED A C 50 audio meter available from the manufacturer Thistype ofoperation must be carried out by qualified technical personnel from the center s maintenance departmentor the distributor sor manufacturer stechnical service department In any case SIBEL S A as manufacturer must authorise in writing at least duringthe period of guarantee andcorresponding technical service in order to be able to carry out this maintenance and will under no circumstances be held responsible for any damage malfunction etc which could result from defective maintenance by personsnot pertainingto SIBEL S A 5 3 CORRECTIVE MAINTENANCE Corrective maintenance refersto leavingthe apparatus in good workingcondition when after malfunction or improper use the apparatus no longer works and needsto be repaired W hen a malfunction which impedes normal use is detected disconnect the machine from the mains and contact SIBEL S A sA fter Sales Service specifyingthe type of problem produced inthe greatest detail possible Ifthe apparatus requires corrective maintenance it is recom
28. d in order to determine auditive thresholds usingmaskingis described below 1 Applyatesttoneto the ear beingtested at the same level asthe auditive threshold without masking Select narrow band noise BN ontheother audio meter channel and apply a maskinglevel at the same level as that ear s auditive threshold Increase the maskingleveluntilthe test tone can no longer be heard or until it exceeds the level ofthe test tone 2 Ifthe test tone is still audible when the noise level isthe same as that ofthe tone this is assumed to be the auditive threshold Ifthe test tone remains masked it isincreased until it can be heard again 3 Increase the noise level by 5 dB Ifthe test tone is inaudible increase its level until it is audible again Repeat the process until the test tone remains audible even when the maskingnoise level has been increased by more than 10 dB This maskinglevel which is the level at which no posterior increase in tone level will be required for audibility isthe correct level for masking and this process should have obtained the correct auditive threshold for the frequency beingtested Record the correct maskinglevel 1 6 3 DETERMINING AU DITIVE THRESHOLDSBY BONE CONDUCTION WITHOUT MASKING TheSIBELMED AC 50 audiometer incorporates the following frequencies and puretone levels for application by bone conduction Hz 250 500 750 1000 1500 2000 3000 4000 Max dB HL 50 60 70 70 70 70 70 70 Min dB HL 10 10 10 10 10 10 10
29. e The advantage ofthistest isthat itis performed ononeear onlyso that the recruitment can be determined where test isnot useful due to symmetrical auditive loss Regardinggeneral requirements the preparation and instruction ofthe patient are similar to those described in section 1 6 1 A and B Particular care should betakento ensure that the mechanics ofthe test in which apuretone of moderated amplitude will be heard are understood by the patient W ith the audiometer prepared as desribed in section 1 4 INSTALLING AND TURNING ON THE AUDIO METER the function is selected in the following manner 1 Press key 12 ontheO PTIO SMEN U Usingkeys and 8the LU SC HER TEST option isselected Enter the test by meansofthe IN TRO key 19 2 The displays will appear similar to the ones below 1999 1998 106 RIGHT LEFT OnlytheMODULATED CONTINUO USandPULSATIN modes theTO NEandN BN functions and the AIR channel will be activated 3 Pressand hold down the IN VER key 19 for afew seconds The displays will look somethinglikethe example below F1F2 3151 F1F2 2 5 J RIGHT LEFT The position correspondingto dB is the modulation amplitude level 0 2 0 3 0 4 0 5 0 6 0 8 1 2 3 40r 5 dB and is selected by means ofthe dB keys of each channel Thecharacterscorrespondingto the frequency indicate the modulation signal frequency which is fixed at 2 5 Hz Releasethe IN VER key
30. e example below AS 1000 1906 pa P 1000 00 1006 H RIGHT LEFT 3 Maintain the IN VER key 9 pressed for some seconds T he displays will now show something like this 12 El r2 1 H sa RIGHT LEFT The position correspondingto dB isthe level of increase 1 2 3 4 or 5 dB and is selected by meansofthe dB keysof each channel Thecharaterscorrespondingto frequency indicatethe interval oftime between increases when in automatic mode 1 2 3 4 5 6 7 8 or 9 seconds or dependingon whenthe SISI key 14 is pressed ifinthe MAN position Selection is done by means ofthe Hz keys 7 and 8 Theremainingcharacters correspond to the description given in section 1 4 3 Select the dB levels and time intervalsto be used Remember that the stimulus counter only works whenthe increases are of 1 dB Releasethe IN VER key 4 Select a working frequency from 500 1000 2000 and 4000 Hz 5 Apply 20 dB above the auditive threshold to thepatient s right channel 6 The displays will appear somethinglike the example below 35 AS 1080 00 1600 60 RIGHT LEFT 7 The increases are applied manually MAN by means ofthe SISI key or automatically dependingon the selection at point W hen in automatic it is also possible to apply extra stimulus usingthe SISI key 8 The test is begun by pressingthe SIGN AL key ofthe channel correspondingto the ear to be examined and maintainingit pressed throughout thetest or by maint
31. e testsor variations dependingon the apparatus W ARBLE STEN GER etc Freefield audiometry 2 2 SIGNALGENERATORS TWO INDEPENDENT CHANNELS Right ear Left ear SIGNAL APPLICATION CHANNELS Air conduction Boneconduction Free field SIGNAL SOURCES Puretones Frequency 125 250 500 750 1000 1500 2000 3000 4000 6000 and 8000 Hz Precision 296 Narrow Band N oise N BN for masking Band D ependingon IEC 645 Attenuation 12 dB octave Modulated frequency MF Carryingfrequency Puretones Modulation frequency 5 Hz 1 Modulation percentage 5 Speech audio metry amplifier Band 250 to 4000 Hz Amplitude A djustable nputs D ynamic microphone A uxilliary input 50 msascendingsignal 200 ms signal 50 ms descendingsignal and 200 mssilence Level gauge LED bar SIGNALPRESENTATION MODES Continuous Pulsatingon all frequencies Frequency 2 Hz 50 msascendingsignal 50 ms descending signal and 200 ms silence Precision 396 Alternatingpulsation The same characteristics as the above but alternating between the right and left channels Modulated amplitude Frequency 2 5 Hz 1 Amplitude modulation 0 2 0 3 0 4 0 5 0 6 0 8 1 2 3 4 or 5 dB Ascendingand descendingtime 50 ms Level gauge LED bar Precision 3 Alternately modulating SISI The same characteristics as the above but alternating between the right and left channels Increase presentation M anual or automatic
32. ed However if only the first segment is lit up thisrepresents a 20 dB decrease in the signal applied 7 Ifthe apparatus has an intercom the hearinglevel of the voice emmited by the patient is adjusted through the technicians earphones The intercom functions whenever SPEECH isin operation 8 The apparatus will now be ready to begin the Speech Audiometry test the end of the chapter Figs 1 13 2 and 1 13 3 show an audiometric file produced by a printer 1 12 PROCEDURE TO BE CARRIED OUT FORFREE AUDIOMETRY As mentioned previously many audio metric tests have different variations in procedure the description of which would be extensive besides incurring errors or omissions For this reason the SIBELMED AC50 audio meter incorporates certain optionsto simplify the performingofthe tests However for specialists for whom the options described are limiting there isan alternative option in which any test desired may be carried out without the limitation of the software whilst remaining within the audiometer s characteristics Thisoptionincluded in the audiometer MUST NOT BECONFUSED W ITH FREEFIELD Byselecting FREE AUDIO METRY the user can carry out any other test includingthose described previously as the audiometer allows access to the selection ofall the functions even though some ofthese may seem irrelevant Note The calibration of FREE FIELD isdone from adistance of 1 meter from the speaker to the central axiswhere the
33. ed with caution 5 2 PREVENTIVE MAINTENANCE Thepreventive maintenance consists ofall the actions designed to keepthe machine in good workingorder Although there are various established models existence there are also certain regulations such as 150 8253 1 which is the mostrecommendable The method to be followed remains at the discretion ofthe specialist However thefollowingchecks are recommended asa minimum 5 2 1 ROUTINE CHECKING AND SUBJECTIVETESTS This check should be carried out on aweekly basis The steps to be followed are desribed below 1 Check that all the contacts are perfectly connected and that the cables and or connectors as well as all other elements do not appear to be broken or damaged externally 2 Check subjectively that the air conduction and bone conduction output is equal on both channels and all frequencies In order to do this 10 or 15 dB just enough to hear is applied The person who carriesout this check should have good hearing 3 Check at a level of 60 dB in AC and 40 dB in BC that there is no distortion noise or parasitic signals in any ofthe frequencies 4 Checkthatthe signal key functions correctly in both direct and indirect mode 5 Checkthatthe attenuator levelsfunction correctly without noisesor interference between channels 6 Checkthe speech audiometry channel and intercom 7 Check that the earphone headband and the vibrator fuction correctly 5 22 OBJECTIVE CHECKING Thische
34. er or to the free field output depending on a code received by the processor 3 2 5 AMPLIFIER The amplifier consists of an operational amplifier and two power complementary transistors which reinforce the signal so that it will be capable of activating the corresponding transducer The right air conduction amplifier receives the signal from the right hand channel and sends it to the right earphone The bone conduction amplifier can receive either the right channel signal or the left channel signal which are sent to the vibrator 3 3 LEFT HAND CHANNEL The left hand channel consists of a set of circuits to treat the signal received from the source and to direct it to the left air conduction channel earphone to the bone conduction vibrator or to the left free field output The left channel is identical to the right and fits the same description as that given previously 3 4 MCROPROCESSOR 3 4 1 PHYSICAL DESRIPTION Themicroprocessor is composed ofaseriesofelectronic mechanisms whichstore manage receive and send out information The main components are Governing program resident 40 Kb ROM 1 Kb 1 024 bytes 16 Kb RAM memory for storage of variables CPU Processing unit Peripherals 3 4 2 PROGRAM The governing program was developed using assembly language to ensure very rapid execution The program manages all the signals which command the analogical plaque reads the keyboard of the apparatus establishes linking pro
35. ess 12 onthe O SMEN U Usingkeys 7 and 8 the SPEECH AUDIO METRY option is selected Enter the test by means of the IN TRO key 19 2 The displays will appear similar to the ones below AC LOGO a AC LOGO RIGHT LEFT onnect the technician s microphone to socket 30 ifthe test will be carried out usingalive voice 1 27 or ataperecorder to socket 29 if recorded material isto be used 4 If the audio meter is installed in a sound proof booth connect the patient s microphone and technician s earphonesto be used for thetestto sockets 25 and 24 5 Inthistest it is convenient to work with the SIGN AL levelsin inverted mode the signal isapplied without pressingthe SIGN AL key in the channel to be used 6 Carry out atrial test by adjustingthe level ofthe signal to be applied to the microphone by means ofthe regulating control 27 so that when the technician emits the words with the microphone at a determined distance the level indicator 5 lights up the whole green area The space between the red and green areas onthe level indicator is equivalent to 0 dB that isto say thereisno increase or lossinthe level ofthe signal applied to the patient It must be taken into account that the level ofthe siganl applied to the patient depends on the level in dB selected for each channel Ifthe speech audiometry signal level indicator 5 is completely lit up this represents a3 dB increase in the signal appli
36. eter automatically sets all the controls and indicators as programmed Seesection 1 4 4 PRO GRAMMIN G THEAUDIO METER 14 3 DESCRIPTION OF DISPLAYS Before beginningthe explanation ofthe vario us audiometric tests it is necessaryto describe the characters which appear in displays 3 left channel and 4 right channel T hese displays show the settings ofthe apparatus at all times Information panel 2 can be used to seethe main characters which appear onthe displaysand their meaning within different audio metrictests Each display is made up of 16 alphanumeric characters T he figure below showsthe appearance ofthe displays the two beingthe same except for a few functions which will be described further on The characters which can be shown on each digit of the display when the apparatus is carrying out an audiometrictest are shown below Thereareother modes mainly for programmingor information which Will be commented upon as necessary asthey come up dB F1F2 F3 lt JKLMAOP RIGHT CHANNEL DISPLAY Thecharacters areas follows ABC Corresponds to the signal level applied to the patient in dB D Free E FIndicates when lit that A signal is beingapplied to the patient Controlled by means of key 10 SIGN AL Correspondsto the application channel and is controlled by means of the F1 key as follows A Air Conduction AC B Bone Conduction BC F Free Field FF Deactivated H X Correspondsto the t
37. ftonal audio verbal the second ofthe T one D ecay Test SISI test and L scher test and the fourth ofthe Fowler and Speech Audio metry test W hen a test is carried out in acertain area that whole area must be printed out therwiseaprintoutisnot possible Atthe end ofthe chapter Figs 1 13 2 and 1 13 3 show an audiometric file produced by aprinter 1 13 2 MEMORISATION OF AUDIOMETERRESULTSIN THEINTERNAL DATABASE TheSIBELM ED AC 50 audiometer incorporatesaRAM memory with acapacityfor the resultsof50 TO N AL AUDIO METRY tests othertypes cannot be memorised This stored information may be used for Transferred afterwards to a PC database or put through an RS 232C channel Printed out through an external printer A MEMORIZING A TEST The process to be followed is the same as that described previously for printing test results in TONAL AUDIO METRY but instead of key 18 key 13 must be pressed B CONSULTING THE REFERENCESSTORED In order to visualise the test numbers and corresponding references which have been memorised it is necessary to exit the test beingcarried out the data for this test being will be lost if it has not been stored beforehand W hen outside test mode before assigninga reference by means of key 110r by pressing key llandresponding Y ES to the ew Patient option without introducingany reference type INTRO W heninthe position described press 13 and the screens will show somethinglike the follo
38. he determining of auditive thresholds by bone conduction should be carried out as described in section 1 6 1 D ETERMIN ING AUDITIVETHRESHO LDS BY AIRCONDUCTION WITHOUT MASKING 1 6 4 DETERMINING AUDITIVE THRESHOLDS BY BONE CONDUCTION WITH MASKING The SIBELMED AC50 audiometer permits masking when determining auditive thresholds by bone conduction without the need to invert the air conduction earphones through which the masking noise is applied The BN levels areas specified in section 1 6 2 Select the channel to be masked usingthe channel used for the bone conduction test Place the vibrator onthe mastoids correspondingto the ear to be examined and ensure the earphones correctly positioned C are must be taken that the transducer s bands do not interfere with one another 1 20 Select each channel by means ofthe follo wing display indications 38 1006 REE RIGHT LEFT In this example the test will first be carried out on the right ear Although election ofthe processand noiseto be applied will be largely effected bythetechnician s personal experience amethod recommended in order to determine auditive thresholds by bone conduction using maskingis described below 1 Apply atest toneto the ear beingtested at the same level as that ofthe auditive threshold without masking Select narrow band noise N BN onthe other audiometer channel and apply amaskinglevel the same as that ear s auditive threshold Increase
39. hen recovered each time the apparatus is switched on Thisinformationiskept in an independently powered solid state internal memory which enablesthe machine to be turned off without its loss The initial programming must be carried out the following manner 1 Set the controlsto the operating position desired when the audio meter is switched on 2 T ype key 12 correspondingto the MENU 3 Select the option STO REPRO GRAM by pressingkey 7upwardsor by pressingkey 8 downwards 4 Type key 191IN TRO From this moment on the audiometer will automatically go to the programmed setting whenever the apparatus is switched on Theonlyfunction which cannot be programmed isthat correspondingto the silencers of each channel 6 and 10 These will alwaysremain inthe direct position the signal will not be applied unless these keys are typed 1 5 AUDIOMETRICTESTS The SIBELMED AC50 audio meter permits the execution of many types of audiometric examination in supraliminar tonal audio metry as well as regular tonal audiometry A MENU containingthe most used examinations has been established to facilitate use ofthe apparatus and if desired printed reports can be produced automatically T his will not prevent the user from fillingin the reports manually or from caryyingout many other tests within the FREE AUD METRY option The tests carried out onthe audiometer are visualised by means of key 12 for the O N SMEN U Keys 7 and 8 are used t
40. hese cases the procedure will be as described in section 1 6 1 to determine the threshold Regarding general aspects the preparation and instruction ofthe patient see section 1 6 1 A and B Inorder to carry outthetest seethe instructions below 1 Select each channel as in the follow ing displays 50 44 AC 1888 1888 RIGHT LEFT In this example the test is begun on the right ear 2 Selectthe frequency and the screening level Theorder in whichto applythe frequency of puretones is asfollows 1000 2000 4000 6000 8000 500 and 250 Hz Some ofthese frequencies may be increased or decreased usingothersincorporated inthe audiometer at the specialist s discretion 3 To begin witha1000H ztoneand a40 dB signal level in order to see that the subject has properly understood theinstructions given If not re instruct him and then repeat the tone Ifthe subject doesnot respond increase thetone level until there is aresponse 4 Adjust the signal level to be applied to the requirements ofthe screening level and applytwo tones with adurationof1to 2 secondsand an interval between of 3 to 5 seconds between each tone If both tonesare perceived the subject he has passed the test for thatfrequency If only onetone is heard apply anew tone Ifthis third tone is heard the subject has passed the test for that frequency Ifthe third tone or the first two tones not heard by the subject he has failed the screeningtest
41. hich the patient s responses more than half ofthe ascensions N ote Ifthe lowest response levels on acertain frequencydiffer morethan 10 dB the auditive threshold must be cosidered suspect and the process must be repeated If there is a difference equal to or over 15 dB between two correlated frequencies the audiometery results must be considered suspect unless they represent asustained incline inthe curve In the case of neurosensorial hypoacusis with a major lossofhigh pitched sounds there tends to be more than 15 dB between two correlative frequencies 1 18 but the curve maintains this tendency 5 Repeat steps 2 3 and 4 for the following frequency Atthe end ofthe chapter Figs 1 13 1 and 1 13 3 show an audio metric file produced by aprinter 1 6 2 DETERMINING AUDITIVETHRESHOLDSBY AIRCONDUCTION WITH MASKING Inorder to avoid thetest tone beingheard by the opposite ear to that which isbeingexamined it is necessary to apply a masking noise to that ear TheSIBELMED AC 50 audiometer incorporates aN arrow oise maskingsystem with the following maskinglevelsto be applied at each frequency usingair conduction Hz 125 250 500 7501000 1500 2000 3000 4000 6000 8000 Max dBHL 60 80 100 100 100 100 100 100 100 100 90 Min dB HL 10 10 10 10 10 10 10 10 10 10 10 HL HearingLevel Although election ofthe process and noise to be applied will be largely effected bythetechnician sexperience a method recommende
42. information panel 2 F3 Selection of source or type of signal accordingto information panel 2 a Attenuator or key used to increase level ofthe signal applied to patient in 5 dB decibel steps Vw Attenuator or key used to diminish the level of signal applied to patient in 5 dB steps SIGN AL Silencer or when activated key which sends or blocksthe signal transmitted to patient depending on mode of direct inverted key 9 11 Keyusedto introduce patient sreference in atestto be printed out memorized inthe machine s internal database or transferred to aPC database 12 OPTION SMEN key usedto select test see patient sreference or to erase incorrectly typed characters 13 Key used to access machine s internal database capable of storingupto fifty audio meter tests 14 SISI Key used to manually create increases in SISI tests 15 RESET K ey used to erase information to be described further on 16 Key used to activate intercom in order to establish dialogue with the patient 177 By means of this key hearing thresholds which have been memorised through the IN TRO 19 key can be visualised 18 Key used to enable the printingofaudio metricfile cards when the thresholds have been memorised previously by means ofthe IN TRO 19 key 19 IN PUT key used to enable storingoftest thresholds as well asto consent selected or input information 1 5
43. isin the following manner Apply a1000 Hz tone by means of keys 7 and 8 Apply alevel which will be clearly audible increase decrease dB keys for example 40 dB for anormal subject Reduce the tone in steps of 20 dB until the patient can no longer hear it Increase the level until it is heard again Emitthetone again at the same level Ifthe patient s response is consistent the check is correct If not repeat the process Thestepsto be followed in order to determine auditive thresholds are as follows 1 The order of application ofthe tones is 1000 1500 2000 3000 4000 6000 8000 750 500 250 and 125 Hz Some ofthese tones can be omitted at the specialist s discretion 2 Applythe tone at 10 dB below the threshold detected duringthe familiarisingtest radually increase the level in 5 dB steps until the patient responds 3 After theresponse reduce the level in 10 dB steps until thereisno response and then beginto increase it again ontinue the process until there are three responses at the same level within amaximum of five ascensions or two responses within three ascensions abreviated method Ifless than three responses every five ascensions or lessthantwo reponses every three ascensions are detected apply atone 10 dB above the level of the last response and repeat the process 4 Inthe graph correspondingto the ear subject to testing record the auditive threshold corresponding to the lowest level at w
44. isrecruitment when one auditive threshold is normal or below 30 dB and the other shows a loss of 25 to 60 dB Thistestisalso called ABLB Alternate Binural Loudness Balance This test may be carried out using models AC 50 B AC50 C and AC50 D 1 5 3 SISI SISI Short Increment Sensitivity Index accordingto Jerger ltconsistsof1 dB increasesofapuretone with anincreasetimeof50 ms adurationof200 msand adecrement of 50 ms The stimulus may be applied either manually or auto matically every 5 seconds This test be done with model AC50 D and also with model A C 50 C ifitthe option isincorporated 1 5 4 TONEDECAY TEST TheTO N EDECAY TEST accordingto CARHART consists of applyinga puretone 5 dB abovethe auditive threshold to the patient and observingwhether it is perceived clearly over a60 second period ormally it will be perceived inthistime If not the level is increased in 5 dB steps until it can be heard and then until itis confirmed to be heard over the period of a minute This test can be carried out using models AC50 B 50 and AC50 D 1 5 5 L SCHERTEST This test consists of the application of a tone of modulated amplitude 40 dB over the threshold and determiningthe modulationthreshold by raisingor loweringthe level ofthe tone the threshold beingfound at the level at which the subject can nolonger hear or begin to hear the modulation ofthe tone This test can be done using models 50 and AC50 D 1 5 6 S
45. it The patient should respond when the toneis heard and stop at the moment when he no longer hearsit The general presentation ofthe sequence oftones W hich ear will be examined first Positioningofthe earphones Glasses and jewelery should be removed if they impedethe correct positioningofthe air or bone conduction earphones Aswell asthisit is advisable to check that hair does not impede the point of contact between the transducers and the outer ear or mastoids Thetechnician will place the air conduction earphones onthe patient checkingthat they are correctly adapted and followingthe code RIGHT ear RED and Left ear 2 BLUE C PREPARING THEAUDIOMETER W ith the audiometer prepared as indicated in section 1 4 INSTALLING AND TURNING ON THE AUDIO METER the functions be selected follows 1 Type key 12 on the OPTIONS MENU By means of keys 7 and 8 select the option TONAL AUDIO METRY and enter the test bytypingthe IN TRO key 19 2 Select each channel with the followingindicationson the displays AC 1 1006 RIGHT LEFT in this example the examination will begin with the right ear EF indicates when lit that the signal is being applied to the patient It is controlled by key 10 SIGN AL Thesignal iscontrolled by meansofthe SIGN AL key Thishas two positions direct and inverted The direct position isused to apply the signal to the patient when the key is pressed
46. l SIBEL S A canapro vide the necessary communication protocol between the audiometer andthe PC SIBEL S A can provide you with sophisticated software to enable the storage and management through aPC ofall information provided by the SIBELMED A C50 Moreover thissoftware permits the visualisation on the computer screen in real time ofthe graphs correspondingto audiometric tests being undergone See the relevant U ser s M anual for details of this option 1 14 AUTOMATIC CALCULATION OF AUDITIVE LOSS The SIBELMED AC50 audiometer auto matically calculates the following parameters when the report is produced through aprinter Percentage of auditive loss Percentage of bilateral auditive loss GLO BAL Average dB of auditive loss Catgorisation of auditive loss ormal Slight Moderate Serious 1 14 1 PERCENTAGE OF AUDITIVELOSS The percentage of auditive loss is determined from atonal audiogram and accordingto the C ouncil of Physical Therapy s 2nd formula A percentage of auditive loss is applied to each ear at the followingfrequencies 500 1000 2000 and 4000 2 dependingon the importance ofthe loss 15 representing500 to 4000 Hz 30 for 1000 H z and 40 for 2000 Hz A 0 loss is considered to be anormal loss and a 100 loss is considered to be cofosis The percentage ofauditive loss for each frequency and intensity level can be found by meansofatable drawn for the organ in question The four values are added togethe
47. levels or the other ear may then be examined FREE AUDIO METRY Thetests completed in this mode cannot be printed through use ofthisoption 4 W henthe auditive thresholds are stored inthetemporary memory they can be visualised to check ondoubtsor errors by holdingdown key 17 and movingthrough the recorded auditive thresholds by means ofthe frequency keys 7 and 8 The figures on the right of the displays show the number corresponding to the type of test being carried out as in the O ptions Menu eg 1 for TONAL AUDIO METRY 2for FO LER TEST etc Therestoftheinformation depends on thetype oftest selected asfollows 1 Tonal Audio metryT hreshold and frequency 2 Fowler TestT hreshold and frequency 3 SISIPercentage and frequency 4 Tone D ecayT estSignal hearingtimes are presented the first position correspondingto 250 1 31 Hz the second to 500 Hz the third to 1000 Hz and the fourth to 2000 Hz 5 L scher T estM odulation threshold and frequency 6 Speech Audio metryT hreshold and percentage of correct replies 5 If athreshold has been introduced incorrectly it is repeated on the corresponding channel and frequency 6 Ifitiswishedto carry out more than one type oftest on same patient it is not neccessaryto print each one separately asthey can be printed together at the end 7 Finalise the test type key 18 and the report will be printed automatically Thereport is divided into three areas the first beingcomposed o
48. mendable to also perform the preventive maintenance described in section 5 2 2 0 BJECTIVECHECKING This requirement should be specified to the technician who is to carry out the reparation as possible breakdowns may entail problems not easily detected without carryingout athorough revision and gauging ofthe apparatus 6 MODIFICATIONS
49. nd correct functioningofthis apparatus only when The premises in which the apparatus is installed complies with the requirements regarding electrical installations UN E IEC includingearthing as well asthe other applicable regulations Reparations servicingand modifications both inside and outside the guarantee period are carried out by SIBEL S A stechnical personnel The machine is used by qualified personnel and accordingto the recommendations in this U ser s M anual 1 3 1 3 DISTRIBUTION OFCONTROLS INDICATORSAND CONNECTIONS 1 3 1 FRONT AND SIDE PANEL Fig 1 3 1 Theaudiometer is controlled by meansofatouch sensitive keyboard situated on the front panel W hen use this keyboard system produces no sound or interference which could distort the signal applied to the patient Many ofthe keyshavetwo functions all of which would betediousto describe in thissection In order to provideaclearer understanding the main function of each key will be described below and the other functions will be described as necessary along with each test All controls indicators and connections which be incorporated in the front and side control panel of the SIBELMED AC50 audio meter will be described below Some ofthem may not exist or be activated in certain models Seesection 1 2 PREVIO USO BSERVATION S I O n off switch 0 O FF Light off I ON Light on 2 Information panel 3 Display correspondingto left channel BLU E
50. o rest Atmospheric Conditions Itisrecommended that the audio meter be installed together with a sound proofbooth inwhich to perform audiometrytests W herethisisnot possible the apparatus must beinstalled in aroom in which the atmospheric noise is sufficiently low so as to not distort test results Failing this N O ISE SU PRESSO RS for the earphones can be adopted OPTION AL B PREPARATING AND INSTRUCTING THE PATIENT Preparingthe patient Ifthe patient has recently been exposed to high noise levels atemporary increase in auditive thresholds may be produced For this reason high noise levels must be avoided before testing or it should be indicated in the report order to avoid errorsasaresult of physical effort it is recommended that the patient arrive at the place oftesting at least five minutes before performingthe test Anotoscopic examination will normally be given by a qualified person in order to see whether there isany obstruction inthe external auditive canal which must be removed Itisabsolutely necessary for the patient to be examined to be comfortably seated calm and alert in order to be able to pay full attention to the test Instructingthe patient The technician doingthe test should explain to the patient what the examination consists of as well as the following The patient must reply when pressingthe patient s response button The patient must respond when he hears the tone not when he only thinks he hears
51. o select the option and the IN TRO key 19 isusedto enter the desired test The options areasfollows SPEECH AUDIO METRY FREEAUDIO METRY 1 TONALAUDIOMETRY 2 FOWLERTEST 3 99 4 TONEDECAY TEST 5 L SCHERTEST 6 7 ithintheMENU thereareother functions which have already been mentioned or which will be mentioned further on such as ERASIN OFTHEDATABASE REPORT FORMAT PRO GRAMMIN G STO RAGE FIN ISHIN G The mechanics neededto carry out some audiometric examinations are explained in this manual There are other methods so it must remain subect to the criteria ofthe specialist which isthe most appropriate method in each case Besidesthese there are other variations ofthetests which are not included The proceduresfor carrying out these tests must be determined by the specialist carryingout the test It isrecommended that persons who are not very familiar with these techniques should consult the relevant literature A brief description of each of the tests presented inthe O PTIO N SMENU isgiven below 1 5 1 TONAL AUDIO METRY Tonalaudiometry is the basic test consistingofthe determiningof ofthe levels of auditory threshold by use of air conduction and bone conduction with and without N BN masking Freefield audiometryisdone asifdealing with tonal audio metry by air conduction This test can be carried out using models 50 B 50 andAC50 D 1 5 2 FOWLERTEST Thistestisdone in order to determine whether there
52. or for signal application by meansofBone Conduction 40 Patient sresponse button attachment 4 d 4 DOODS v zzo s CEI a hl E o Fig 1 32 1 8 14 INSTALLING AND TURNING ONTHEAUDIOMETER 1 4 1 INSTALLINGTHE AUDIOMETER Inaccordance with the type of protection against electric shocks established inthe regulation UN E 20 613 IEC 601 1 the SIBELMED AC50 audiometer is listed as aC LASS 1 machine The SIBELMED AC 50 audio meter requires 220V and 50 60 Hz 10 mains terminal X X X X with its correspondingearth terminal in compliance with the UN E IEC regulations currently in effect T he required power must be below 40 VA Therequired atmospheric conditions are Storage temperature from 0 to 60 Atmospheric temperature between 10 and 40 Relative humidity below 90 vvithout condensation The mains cable which is included incorporates an earth yellow green asit isrequiredthat the audiometer like any other C LASS 1 electro medical apparatus be connected to earth Itisrecommendedthatthe audiometer beinstalled together with a sound proof booth for audiometrytests W herethisisnot possible the machine must beinstalledinaroom inwhich the atmospheric
53. r one per frequency for each ear in order to obtain the total percentage for each ear Example Rightear 500 1000 2000 4000 Right total loss LossindB 15 10 5 10 05 03 0 01 0 9 Leftear 500 1000 2000 4000 Left total loss LossindB 35 30 40 50 36 54 129 8 0 29 9 1 14 2 PERCENTAGE OF BILATERAL AUDITIVE LOSS GCOBAL If the user desires to know the global percentage of bilateral auditive loss the average is calculated by multiplyingthe percentage ofthe best ear by seven addingthisto the percentage ofthe poorer ear and dividing the total by eight By doing this the best ear is given priority which is important regarding inability in communication loss in best ear x 7 loss poorer ear bilater al loss 8 fromthe previous example 0 9 x 7 4 29 9 4 5 bilateral auditive loss 8 1 14 3 AVERAGE AUDITIVE LOSSIN dB The number of dB loss in the frequencies 500 1000 2000 and 4000 are added together and then divided byfour Followingfromthe previous example Right ear 15 10 5 10 4 10 dB average auditive loss Left ear 35 30 40 50 4 38 dB average auditive loss 1 14 4 CATEGORIZATION OF AUDITIVE LOSS The categorization regardingthe auditive lossof each ear is as follows NORMAL 0 to 10 of auditive loss SLIGHT HEARING IMPAIRED 1110 30 MODERATE HIPO ACUSIS 3lto 60 SERIO U SHIPO ACUSIS 61to 100 AUDIOMETRIC EXAM t3 X EELmED ACIO Date
54. rom the 11 recommended in the regulations This generator produces pure tones at a constant level for posterior dosage by the Amplitude Modulator and the Attenuator An auxilliary circuit in the tone generator permits the modulation of the frequency ofthe tones within determined margins in accordance with the signals received by the processor 3 1 2 SPEECH AUDIOMETRY Optional The application of verbal sounds in order to evaluate intelligibility in conversation is done by amplifying the signals produced by the microphone in turn produced by the monitor technician carrying out the test to the level necessary for Speech Audiometry tests The level gauge orientates the monitor in order to maintain a regular level of voice intensity so that the dB values received by the patient are maintained within determined margins 3 1 3 NARROW BAND NOISE Thesourceofthisnoise isaW hite N oise generator Thetonalities produced which are slightly different from the tones themselves are attenuated from the white noise generator s signal by means of a filter synchronised with the frequencyselector This noise is useful for masking a tone in one ear 3 1 3 1 4 VOCAL NOISE The vocal source of the noise is the same W hite N oise generator and by means of a low pass filter followed by aX XXX filter the tonality band corresponding to voice noise is selected and the other bands attenuated 3 1 5 SOURCE SELECTOR This element consists of two identi
55. the maskinglevel until the test tone can no longer be heard or until it exceeds the level ofthe test tone by 40 dB 2 Ifthe test tone is still audible when the noise level is 40 dB above the test tone this is assumed to be the auditive threshold Ifthe test tone remains masked it is increased until it is heard once again 3 Increase the noise level by 5 dB Ifthe test tone is inaudible increase its level until it is audible again Repeat the process until the test tone remains audible even when the maskingnoise level has been increased by more than 10 dB T his maskinglevel which is the level at which no posterior increase in tone level will be required for audibility isthe correct level for masking and this process should have obtained the correct auditive threshold for frequencytested Record the correct maskinglevel 1 6 5 SCREENING AUDIOMETRY This type oftest is used in cases where the aim is not to find the subject s auditive threshold but rather to determine whether or not he can hear certain levels This method is simple and easy to perform Screening audiometry is atest based on determining whether a patient has as auditive threshold the same better or worse than the established screening level These screening levels are at the specialist s discretion Screening audiometry can be completed by determiningthe auditive threshold of frequencies for which the patient has failed the screening test In t
56. tocol through the RS channel manages the output to an external printer Centronics parallel etc 3 4 3 RAM MEMORY 3 3 The variables used in the program and other variables which define states of the audiometer such as the initial programming the gauging tables etc are stored in the memory This memory is powered by aN i Cd battery in order to avoid the loss of data when the apparatus is switched off 3 4 4 CPU The CPU isadevice which manages and carries out instructions contained within the program A 65C 02 is used with a clock frequency of 1 Mhz 3 4 5 PERIPHERALS The CPU unit communicates with its environment by means of VIA 6522 s an ACIA 6551 and 74LS374 latches The VIA 6522 s control the keyboard printer modulators etc the ACIA 6551 controls communications by means of the RS channel and the 7415374 latches control the attenuators and silencers 3 5 INTERCOM Optional The intercom consists of a circuit which enables the patient to be heard by the monitor while he is situated in an audiometric cabin or in a different room from to that in which the audiometer is placed The signal proceeding from the patient s microphone is received during the pre amplifier stage and its level is conveniently raised The level achieved can then be controlled manually by means of a volume control This signal can be connected or disconnected in accord with the control signals from the processor by means of an analogical selector
57. vel must be correct before pressing IN TRO NOTICE The memorizationisdone independentlyfor each threshold and maskinglevel if 1 30 one is used The apparatus will only store the last threshold detected before pressingINTRO FO W LER TEST For thistest thethresholdscorrespondingto each channel for which the patient indicates that he hears the same level in both ears are stored A signal must have been applied to both ears simultaneo uo usly The dB level indicators are situated correctly and IN TRO is pressed SISI For thistest once the twenty 1 dB signal increases have been applied and the patient has given the correspondingresponses ifhe has heard with the data detected in the increase and response counters IN TRO ispressed TONEDECAY TEST Inthetone D ecaytestthe patient gives his responses by means ofthe response button while he hears the signal W hen he no longer hears it he releases the button At that moment the technician typesthe IN TRO key 19 in order to record the hearingtime LUSCHER TEST Inthiscasethe procedure for storingthresholdsisthe same as that used for Tonal Audiometry SPEECH AUDIO METRY For speech audiometry the number of wordstransmitted to and received fromthe patient are fixed at adetermined level W ith the level selector correctly set INTRO is pressed and the audiometer will request the number of words applied and correct responses hisinformation is introduced and IN TRO is pressed ther
58. wing example dB F1F2 F3 SISI dB F1F2 F3 SAVED TEST 16 REF 61463 RIGHT LEFT By holding down key 13 the references memorised may be visualised by means of keys 7 and 8 C TRANSFERRING THE INFORMATION TO A PC DATABASE In order to transfer the tests stored in the Internal D atabase to a PC it is necessary to possess the PC DATABASE option developed by SIBELS A otherwise the user must effect the application needed Inthe first case the process to be followed for the transference is described in the User s Manual ofthat option D PRINTING ONE OF THE MEMORISEDTESTS The tests memorised can be printed one by one To do this keys 13 and 18 must be typed in that order and held down until printingbegins E ERASING THE INTERNAL DATABASE The option ERASE DATABASE canbe found inthe O PTIO SMEN U key 12 IftheIN TRO keyistyped when in this position the user will be asked whether he wantsto erase the memorised information Ifthe reply is affirmative all the information the Internal D atabase is erased 1 13 3 EXTERNAL DATABASE AND RS 232C CHANNEL TheSIBELMED AC 50audiometer incorporates atype RS 232C type communication channel which can be connected through socket 37 This channel permits information stored in the internal database to be transferred to acomputer as well as communication in real time with an EX TERN ALDATABA SE Ifthe user wishesto develop any particular application to be used through this channe
59. ype of signal emmited and is controlled by means ofthe F2 key as follows C Continuos signal P Pulsatingsignal P Intermittent Pulsatingsignalalternating between left and right channels M Modulated volume signal MV M Intermittent Modulated volume signal alternating between left and right channels S 99 mode signal Deactivated Free JKLM Correspondsto thesourceor typeofsignal used and iscontrolled by meansofthe F3 keyasfollows XXXX Frequency in Hz of PureTone NBN Masking with narrow band noise SN Maskingwith speech noise SPE Speech audio metry XXXX Intermittent Pure tone in H z with modulated frequency N Free Corresponds to the number of 1 dB increases sent to patient SISI mode LEFT CHANNELDISPLAY Display correspondingto the left channel isidentical to the right one except regardingthe O P characters which correspond to the number ofstimulus detected inthe patient and when in SISI modeinthe TON E DECAY test correspondsto seconds during which the patient has heard the signal 1 4 4 PROGRAMMING THE AUDIO METER Any apparatus possessingahigh number offunctions can be manipulated voluntarily or involuntarily by athird party so alteringthe standard programmingofthe controls thereby compromisingtheir convenient use n order to make up for thisshortcoming the SIBELM ED A C 50 audiometer is provided with a programming facility which enables the user to define the initial workingprogram which ist

AUDIOMETER AC50

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