Frye FONIX 6500-CX Workbook Download Page 1

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FM SYSTEMS

with the FONIX 6500-CX

Hearing Aid Analyzer

(Requires software version 4.20 or above)

FRYE

FRYE ELECTRONICS, INC.

P.O. Box 23391 • Tigard, OR 97281-3391

(503) 620-2722 • (800) 547-8209

Fax: (503) 639-0128

www.frye.com • e-mail: [email protected]

Summary of Contents for FONIX 6500-CX

Page 1: ...S with the FONIX 6500 CX Hearing Aid Analyzer Requires software version 4 20 or above FRYE FRYE ELECTRONICS INC P O Box 23391 Tigard OR 97281 3391 503 620 2722 800 547 8209 Fax 503 639 0128 www frye com e mail sales frye com ...

Page 2: ...3 4 Test aid alone with typical input EHA65 17 1 3 5 Test FM ENV microphones with typical input to FM microphone EFE80 18 1 3 6 Test environmental microphone response with typical input EEF65 20 1 3 7 Test aid alone with high level input EHA90 21 1 3 8 Test with FM system using a high level input EFE90 21 1 3 9 Test environmental mic response with high level input EEF90 23 1 4 Coupler Setup in the...

Page 3: ...al microphone on a hearing aid 45 2 2 Testing FM Only 46 2 2 1 Test aid with typical input RHA65 46 2 2 2 Test FM system with typical input RFM80 47 2 2 3 Test aid with high level input RHA90 48 2 2 4 Test FM system with high level input RFM90 49 2 3 Testing FM ENV 50 2 3 1 Single frequency output of hearing aid 50 2 3 2 Single frequency response of FM mic at 65 dB SPL 51 2 3 3 Verify increase in ...

Page 4: ... mouth of the talker whereas with hearing aids the pickup microphone is worn by the listener typically at a minimum of 3 ft 1 m from the talker This difference affects both the level and the frequency content of typical input signals With FM systems typical speech input levels range from 75 to 85 dB SPL as compared with 60 to 70 dB SPL for hearing aids With the chest worn loca tion of the pickup m...

Page 5: ...both test conditions omit the 2 cc coupler tests For both 2 cc coupler and real ear tests 1 Test the user s hearing aid with typical input signal levels 2 Test the FM system with typical input signal levels and make any necessary adjust ments 3 Test the user s hearing aid with high input signal levels 4 Test the FM system with high input signal levels and make any necessary adjust ments Curve Labe...

Page 6: ...orresponding sets of real ear measurements of FM systems Section 1 contains four different sets of testing procedures but you only need to follow the testing procedure suitable for the FM system being tested Section 2 contains two different sets of testing procedures Likewise you only need to follow the real ear procedures suitable for the FM system Ideally you should perform one set of coupler me...

Page 7: ...i directional Testing FM ENV If the FM receiver or hearing aid is directional or cannot fit inside the sound chamber and The FM receiver is primarily set to receive FM only signals follow the procedures described in Section 1 5 Directional Testing FM only The FM receiver is primarily set to receive FM with environmental signals FM ENV follow the procedures described in Section 1 6 Directional Test...

Page 8: ...ecessary 2 Attach the BTE hearing aid to the HA 2 coupler 3 Place the coupler hearing aid assembly on a foam pad outside the test box 2 ft 60 cm from the transmitter during testing BTE aid with silhouette coil Figure 1 1 1C 1 Attach the ear level adapter to the HA 2 coupler if necessary 2 Attach the BTE hearing aid to the HA 2 coupler 3 Place the coupler hearing aid assembly on a foam pad outside ...

Page 9: ... required separation 2 ft 60 cm from the transmitter It may be necessary to turn the analyzer s video monitor off during test ing 2 Place the neck loop around the listener s neck or around the neck of a person of sim ilar size 3 Attach the listener s hearing aid to the HA 2 coupler 4 While holding the coupler in hand place the hearing aid at the listener s ear as typi cally worn 5 Take care not to...

Page 10: ...the coupler 4 Place the assembly into the sound chamber 5 Close and latch the sound chamber door Figure 1 1 2 Hearing aid setup with FM boot 1 1 3 FM System 1 Make sure the sound chamber is leveled 2 Set the FM receiver to receive FM only 3 Insert the coupler microphone into the HA 2 coupler and attach the output of the FM receiver as explained in Section 1 1 1 and place at least 2 ft 60 cm from a...

Page 11: ...above 2 Set the FM receiver to receive FM only 3 Observe the RMS OUT for this FM only signal 4 Set the FM receiver to receive FM ENV 5 Observe the RMS OUT for the FM ENV setting If the RMS OUT is more than 3 dB higher for FM ENV than for FM only then you will need to isolate the environmen tal microphone when testing the FM microphone in FM ENV mode If the RMS OUT for both signals is within 3 dB n...

Page 12: ...el FM receiver to the HA 2 coupler and set it to receive input from the environmental microphone only 3 Insert the coupler microphone into the HA 2 coupler 4 Place the ear level receiver and coupler at the test position in the sound chamber 5 Close and latch the sound chamber lid 6 You are now ready to test the FM system with the signal delivered to the environ mental microphone Shoebox lined with...

Page 13: ...2 coupler outside the sound chamber as described in Section 1 1 1 3 Insert the coupler microphone into the HA 2 coupler 4 Place the lapel microphone from the FM receiver at the test position in the sound chamber See Figure 1 1 4 5 Close and latch the lid of the sound chamber 6 You are now ready to test the FM system with the signal delivered to the environ mental microphone Figure 1 1 4 Testing la...

Page 14: ...t aid alone with typical input EHA65 1 Set up the hearing aid according to the hearing aid setup described in Section 1 1 2 2 Press RESET to enter Composite Weighted Gain Mode 3 Press WEIGHT to enter Composite Weighted Power Mode The display will be labeled as OUTPUT SPL 4 Use to set RMS Source to 65 dB SPL 5 Once the curve is stable press FREEZE to pause the measurement If the 6500 CX has the Mul...

Page 15: ...EEZE and START to save the curve as you did in Section 1 2 1 4 To view the EFM80 and EHA65 on the same screen requires the Multi Curve Option a Press MULTI b Highlight MULTIPLE CURVES c Press START d If necessary use to display CRV 1 in the first slot This curve is EFM80 e Use to select the second slot f If necessary use to display CRV 2 in the second slot This curve is EHA65 See Figure 1 2 2 If y...

Page 16: ...nd therapists must be made aware that when the FM system is used the settings on the hearing aid must be changed for optimum per formances 1 2 3 Test aid alone with high level input EHA90 1 Turn off the FM signal and set up the hearing aid for testing as described in the hearing aid setup in Section 1 1 2 2 Press SINE COMPOSITE button to enter Pure Tone Mode The analyzer will auto matically set it...

Page 17: ...s without the Multi Curve option press CRT to print a hardcopy 3 This response will be referred to as the Electroacoustic FM Saturation Response or EFM90 Figure 1 2 4 Comparison of EHA90 CRV2 the hearing aid response at 90 dB SPL with EFM90 CRV1 the FM response at 90 dB 4 To view both curves on the same screen requires the Multi Curve Option a Press MULTI b Highlight MULTIPLE CURVES c Press START ...

Page 18: ...t EFE90 and com pare it to EHA90 5 If EFM90 is greater than 5 dB above or 10 dB below EHA90 adjust the maximum output control if possible on the FM receiver or on the hearing aid if necessary If the hearing aid is adjusted the teacher parents and therapists must be made aware that when the FM system is used the settings on the hearing aid must be changed for optimum performances For mild to modera...

Page 19: ...ic response of the FM transmitter receiver EEF65 typical electroacoustic response of environmental microphone EHA90 saturation electroacoustic response of the aid EFE90 saturation electroacoustic response of the FM transmitter receiver EEF90 saturation electroacoustic response of environmental microphone 1 3 1 Single frequency output of omni directional hearing aid in the sound chamber 1 Set up th...

Page 20: ...iver attached to the 2 cc coupler and set to receive FM ENV 2 Press repeatedly to increase the signal level to 80 dB SPL 3 Look at the AID OUT on the screen This is the new FM OUTPUT 4 Compare the HEARING AID OUTPUT found in Section 1 3 1 to this new FM OUT PUT and adjust the FM receiver volume control according to the following If the increase is 10 dB no further adjustments are necessary 15 dB r...

Page 21: ...re 1 3 4 1 3 5 Test FM ENV microphones with typical input to FM microphone EFE80 1 Set up the FM system according to Section 1 1 3 The FM receiver should be set to receive FM ENV 2 Use to adjust the signal level to 80 dB SPL 3 This curve will be referred to as the Electroacoustic FM Response or EFE80 4 To view the EFE80 and EHA65 on the same screen requires the Multi Curve Option a Press MULTI b H...

Page 22: ...are EHA65 CRV 2 to EFE80 CRV 1 to confirm that the desired FM advan tage is maintained over the 500 to 2000 Hz range In general that advantage should be 7 10 dB See Figure 1 3 5 6 For units with Multi Curve you will want to save EFE80 for a comparison in the next section To do this a Press CONTINUE twice to exit from Multi Curve b Press FREEZE to save the current EFE80 measurement c Press START to...

Page 23: ... from Section 1 3 4 and EFE80 from Section 1 3 5 If you have Multi Curve do the following a Press MULTI b Highlight MULTIPLE CURVES c Press START d CRV 1 will be selected for the first Multi Curve slot This is the EEF65 response CRV 2 should be selected for the second Multi Curve slot This is the EFE80 response Use to select the third Multi Curve slot e Use to select CRV 3 for the third Multi Curv...

Page 24: ...print a hardcopy 4 This response will be referred to as the Electroacoustic Hearing Aid Saturation Response or EHA90 See Figure 1 3 7 Figure 1 3 7 EHA90 the hearing aid response at 90 dB SPL 1 3 8 Test with FM system using a high level input EFE90 1 Set up the FM system for testing according to Section 1 1 3 The FM receiver should be set to receive FM ENV 2 Press START to begin the pure tone sweep...

Page 25: ...cond slot This curve is EHA90 g You may want to press and FREEZE to turn off the display of CRV 3 since it is not relevant to this comparison Similarly press and FREEZE again to turn off the display of CRV 4 If you don t have the Multi Curve Option press CRT to print out EFE90 and compare it to EHA90 5 If EFE90 is greater than 5 dB above EHA90 adjust the FM system to obtain a better match As a las...

Page 26: ...PL input to the environmental microphone 4 To view both curves on the same screen requires the Multi Curve Option a Press MULTI b Highlight MULTIPLE CURVES c Press START d EEF90 CRV 1 should be displayed in the first slot and EFE90 CRV 2 should be displayed in the second slot e Press to select the third slot f If necessary press to select CRV 3 for the third slot This is the EHA90 measurement 5 Co...

Page 27: ... described in this section will be performed on the remote module 2 Affix the reference microphone with Fun Tak to the platform at the top of the floor stand 6 inches 15 cm in front of the sound field speaker with the microphone pointing toward the speaker See Figure 1 4 1A If you don t have a floor stand the back of a chair can suffice But be sure the chair is facing to the side of the setup to a...

Page 28: ...tube should extend 1 2 mm past the other end of the adapter Use Fun Tak to secure the probe tube to the adapter See Figure 1 4 1B Figure 1 4 1B Thread probe tube through probe mic adapter 8 Insert the adapter into the HA 2 coupler and attach the probe tube to the probe microphone See Figure 1 4 1C Figure 1 4 1C Attach coupler to probe mic Probe mic Probe mic adapter ...

Page 29: ...field speaker If you are testing out of order follow the instructions found in Section 1 4 1 Steps 1 4 to level the sound field before testing 1 Place the FM transmitting microphone on the floor stand six inches 15 cm from the sound field speaker Keep all sound entry ports clear of the platform Place the transmitter and its cord behind the transmitting microphone 2 Thread a probe tube through the ...

Page 30: ... FM setup described in Section 1 4 1 However if you are testing in a noisy environment you may want to isolate the environmental microphone from the room noise To check if you need to provide sound isolation for the environmental microphone when testing the FM microphone in FM ENV mode do this procedure 1 Set the FM microphone up for testing as described in Section 1 1 3 2 Set the FM receiver to r...

Page 31: ...r Real Ear Mode by pressing START STOP on the remote module or PROBE on the 6500 CX main module 2 Affix the FM receiver to the platform stand in the manner shown in Figure 1 4 3A Figure 1 4 3A Attaching reference microphone 3 Using Fun Tak affix the reference microphone to the receiving unit so the entrance to the reference microphone is very close to that of the environmental microphone 4 Place t...

Page 32: ...the adapter and probe tube attached to the probe microphone into the HA 2 coupler and attach to the button earphone direct audio input hearing aid or aid coupled with neck loop or silhouette as explained in Section 1 1 10 You are now ready to test the FM system with the signal delivered to the environ mental microphone Figure 1 4 3B Leveling the sound field Figure 1 4 3C Testing with body worn rec...

Page 33: ...nsmitter receiver 1 5 1 Test aid alone with typical input EHA65 1 Follow the hearing aid setup instructions found in Section 1 4 1 to set up the hearing aid for testing the sound field enter Real Ear Mode and level the sound field speak er The FM transmitter should not be on and the aid should be set to receive the hearing aid microphone 2 Press MENU on the remote module 3 Press to highlight CREAT...

Page 34: ...has stabilized This curve is the Electroacoustic Hearing Aid Response or EHA65 See Figure 1 5 1 1 5 2 Test FM microphone with typical input EFM80 1 Set up the FM system for testing according to FM setup described in Section 1 4 2 2 Use to select CRV 2 3 Use to set the RMS source to 80 dB SPL 4 Press START STOP to start the measurement 5 Once the measurement stabilizes press START STOP again to sto...

Page 35: ... aids adjust the settings on the hearing aid as a final step if necessary If this must be done the teacher parents and therapists must be made aware that when the FM system is used the settings on the hearing aid must be changed for optimum per formances See Figure 1 5 2 77 1 5 3 Test aid alone with high level input EHA90 1 Set up the hearing aid for testing in the sound field by following the dir...

Page 36: ...rement 5 CRV 2 is now the Electroacoustic FM Saturation Response or EFM90 6 Compare EHA90 CRV 1 to EFM90 CRV 2 If EFM90 is greater than 5 dB above or 10 dB below EHA90 adjust the maximum output control if possible on the FM receiver or on the hearing aid if necessary If the hearing aid is adjusted the teacher parents and therapists must be made aware that when the FM system is used the settings on...

Page 37: ...lectroacoustic response of the FM transmitter receiver EEF65 typical electroacoustic response of environmental microphone EHA90 saturation electroacoustic response of the aid EFE90 saturation electroacoustic response of the FM transmitter receiver EEF90 saturation electroacoustic response of environmental microphone 1 6 1 Single frequency output of hearing aid 1 Set up the aid for testing accordin...

Page 38: ... FM OUTPUT is matched to the HEAR ING AID OUTPUT found in Section 1 6 1 This matches the gain of the FM system and the hearing aid 6 Press START STOP to turn off the signal 1 6 3 Verify increase in signal level 1 Leave the FM system and the analyzer set up as described in Section 1 6 2 2 Press START STOP to start the single frequency measurement 3 Press repeatedly to increase the signal level to 8...

Page 39: ...ote module 3 Press to highlight CREATE TARGET 4 Press to select SPL TARGET 5 Press START STOP twice This will open the SPL Test Screen 6 Look in the bottom left corner of your screen If it says AUTO press UNAIDED on the remote module This will put you in MANUAL Mode 7 Press MENU to enter the SPL Menu 8 Select COMP for AIDED CURVE 1 AIDED CURVE 2 and AIDED CURVE 3 9 Press MENU to return to the SPL ...

Page 40: ...und field speaker you can skip to step 5 in that section 2 Use to select CRV 2 3 Use to set the RMS source to 80 dB SPL 4 Press START STOP to start the measurement 5 Once the measurement stabilizes press START STOP again to stop the measure ment 6 CRV 2 is now the EFE80 or the Electroacoustic FM and Environmental Response with 80 dB input to the FM microphone 7 Compare EHA65 CRV 2 to EFE80 CRV 1 t...

Page 41: ...ress to set the source level to 65 dB SPL 4 Press START STOP to start the measurement 5 When the measurement has stabilized press START STOP again to stop the meas urement This measurement will be referred to as EEF65 6 Compare all three curves CRV 1 should be EHA65 CRV 2 should be EFE80 and CRV 3 should be EEF65 For a successful fit EHA65 and EEF65 should be similar and EFE80 should be 7 10 dB hi...

Page 42: ...you can skip to step 6 in that section 2 Press MENU to enter the SPL Menu 3 Select PURE TONE for AIDED CURVE 1 AIDED CURVE 2 and AIDED CURVE 3 4 Press MENU to return to the SPL Test Screen 5 Press to select CRV 1 6 Use to select a source level of 90 dB SPL 7 Press START STOP to begin the sweep 8 This response will be referred to as the Electroacoustic Hearing Aid Saturation Response or EHA90 See F...

Page 43: ...ss START STOP to make the measurement 5 CRV 2 is now the Electroacoustic FM Saturation Response or EFE90 6 Compare EHA90 CRV 1 to EFE90 CRV 2 See Figure 1 6 8 If EFE90 is greater than 5 dB above EHA90 adjust the FM system to obtain a better match As a last resort adjust the settings on the hearing aid If this must be done the teacher par ents and therapists must be made aware that when the FM syst...

Page 44: ...veled you don t have to re level it 2 Press to select CRV 3 3 Press START STOP to take the measurement 4 This measurement will be referred to as EEF90 or the Electroacoustic FM and Environmental Response with 90 dB SPL input to the environmental microphone 5 Compare EEF90 CRV 3 to EFE90 CRV 2 and EHA90 CRV 1 All three curves should match See Figure 1 6 9 Figure 1 6 9 Comparison of EHA90 EFM90 and ...

Page 45: ...low the procedures described in Section 2 3 Testing FM ENV Both of these procedures will work with directional microphones 2 1 Setup This section describes the real ear setup for testing the hearing aid FM system and environ mental microphone in a sound field using a probe microphone 2 1 1 Hearing Aids 1 Place the sound field speaker 12 15 inches from the client pointing towards his head at a 45º ...

Page 46: ...ribed sets of tests it is assumed that the analyzer is already in Real Ear Mode 1 Place the reference microphone on a platform at the top of a floor stand 6 inches 15 cm in front of and facing the loudspeaker as in Figure 2 1 2A 2 Choose a place to stand during testing preferably away from the loudspeaker and microphone Hold the remote module so you can operate the test Stand precisely in this pla...

Page 47: ...client uses an environmental microphone with his FM system it is important to test it to make sure that its response matches that of the client s hearing aid This section describes several different methods for setting up an environmental microphone for testing 6 inches FM transmitter Probe mic and FM receiver Patient out of sound field 6 inches Reference mic ...

Page 48: ...nd field speaker 4 Remove the reference microphone from the sound field It will not be used for test ing so you can lay it to one side 5 Mark the probe tube to ensure the desired insertion depth and place it and the ear piece of the receiving unit in the client s ear The insertion depth of the probe tube should be the same as used to test the client s hearing aid The client should be at least 2 ft...

Page 49: ...ar saturation response of the FM transmitter receiver 2 2 1 Test aid with typical input RHA65 1 Press START STOP on the remote module or PROBE on the main module to enter Real ear Mode 2 Follow the instructions in Section 2 1 1 to level the sound field speaker and ready the client for a real ear measurement 3 Press MENU Figure 2 2 1 RHA65 hearing aid response at 65 dB SPL 4 Highlight CREATE TARGET...

Page 50: ...ent has stabilized press START STOP again to stop it 15 This curve will be referred to as the Real Ear Hearing Aid Response or RHA65 See Figure 2 2 1 2 2 2 Test FM system with typical input RFM80 1 Set up and level the FM system according to Section 2 1 2 The environmental micro phone on the FM receiver should be off 2 Use to select CRV 2 3 Use to adjust the amplitude of CRV 2 to 80 dB SPL Figure ...

Page 51: ...djust the FM volume control As a last resort adjust the settings on the hearing aid and inform the teacher parents and therapists that when the FM system is used the settings on the hearing aid must be changed for optimum performance 2 2 3 Test aid with high level input RHA90 1 If you followed the instructions from Sections 2 2 1 and 2 2 2 you will be in the SPL Test Screen 2 Press MENU 3 Select P...

Page 52: ... be off 2 Use to select CRV 2 3 Use to adjust the amplitude of CRV 2 to 90 dB SPL 4 Press START STOP to take measurement 5 This curve will be referred to as the Real Ear FM Saturation Response or RFM90 6 Compare RHA90 CRV 1 and RFM90 CRV 2 If necessary adjust the FM volume control to obtain a better match As a last resort adjust the settings of the hearing aid If this must be done the teacher pare...

Page 53: ...l ear response of the aid RFE80 typical real ear response of the FM transmitter receiver REF65 typical real ear response of environmental microphone RHA90 saturation real ear response of the aid RFE90 saturation real ear response of the FM transmitter receiver REF90 saturation real ear response of environmental microphone 2 3 1 Single frequency output of hearing aid 1 Press RESET on the main modul...

Page 54: ...FM ENV 2 Press START STOP to begin a single tone continuous measurement 3 Note the MIC OUT reading in the CURRENT STATUS box This is the FM Output 4 Adjust the FM receiver volume control so that the FM Output matches the Hearing Aid Output found in Section 2 3 1 Now the gain of the hearing aid and the FM sys tem have been matched 5 Press START STOP to stop the measurement 2 3 3 Verify increase in ...

Page 55: ...tion 2 1 1 Make sure to level the sound field speaker 2 Press MENU to enter the Quik Probe II Menu 2 Highlight CREATE TARGET using 3 Select SPL TARGET using 4 Press START STOP twice This will open the SPL Test Screen Figure 2 3 4 RHA real ear response of hearing aid 5 Make sure that the bottom left corner of your screen says MANUAL If it says AUTO press UNAIDED to change it to MANUAL 6 Press MENU ...

Page 56: ...el the sound field speaker 2 Use to select CRV 2 3 Use to adjust the amplitude of CRV 2 to 80 dB SPL 4 Press START STOP to begin measurement Press it again once a stable response is observed 5 This curve will be referred to as RFE80 or the Real Ear FM and Environmental Response with 80 dB SPL input delivered to the FM microphone 6 Compare RHA65 CRV 1 to RFM80 CRV 2 and confirm that the desired FM ...

Page 57: ...level of 65 dB SPL 4 Press START STOP to start the measurement and again once the measurement has stabilized 5 This measurement will be referred to as REF65 or the Real Ear FM and Environmental Response with 65 dB SPL input delivered to the environmental microphone 6 Compare RHA65 CRV 1 to RFE80 CRV 2 and REF65 CRV 3 RHA65 and REF65 should be similar while RFE80 should give a 7 10 dB advantage See...

Page 58: ...From the SPL Test Screen press MENU 3 Select PT_BURST for AIDED CURVE 1 AIDED CURVE 2 and AIDED CURVE 3 4 Press MENU to return to the SPL Test Screen 5 Press to select CRV 1 6 Use to adjust the source level to 90 dB SPL 7 Press START STOP to take measurement 8 This curve will be referred to as the Real Ear Hearing Aid Saturation Response or RHA90 See Figure 2 3 7 Figure 2 3 7 RHA90 Real Ear Satura...

Page 59: ...ponse with 90 dB SPL input delivered to the FM microphone See Figure 2 3 8 6 If RFM90 is greater than 5 dB above RHA90 adjust the FM controls to obtain a better match As a last resort adjust the settings on the hearing aid If this must be done the teacher parents and therapists must be made aware that when the FM system is used the settings on the hearing aid must be changed for optimum performanc...

Page 60: ...field speaker 2 Press to select CRV 3 3 Use to adjust the source level of CRV 3 to 90 dB SPL 4 Press START STOP to take the measurement 5 This response curve will be referred to as REF90 or the Real Ear FM and Environmental Response with 90 dB SPL input to the environmental microphone See Figure 2 3 9 6 Compare RHA90 CRV 1 RFE90 CRV 2 and REF90 CRV 3 All three responses should match Figure 2 3 9 C...

Page 61: ...al Response with 90 dB SPL input to the FM microphone EEF90 Electroacoustic FM and Environmental Response with 90 dB SPL input to the Environmental microphone Real Ear Measurement Labels RHA65 Real Ear Hearing Aid Response with 65 dB SPL input RFM80 Real Ear FM Response with 80 dB SPL input RHA90 Real Ear Hearing Aid Saturation Response with 90 dB SPL input RFM90 Real Ear FM Saturation Response wi...

Page 62: ...iversity of Texas at Dallas For further study of methods and procedures for testing FM systems and auditory trainers the reader is referred to the following resources American Speech Language Hearing Association 1999 In Press Guidelines for Fitting and Monitoring FM Systems Cornelisse LE Gagné J P and Seewald RC Long term average speech spectrum at the chest level microphone location Journal of Sp...

Page 63: ...60 Testing FM Systems with FONIX 6500 CX Analyzers ...

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