fitting and evaluation of fm systems for ha users

Fitting and Fitting and Evaluation of FM Evaluation of FM Systems for HA Systems for HA

Users Users

Guidelines for Fitting and Guidelines for Fitting and EvaluationEvaluation

ANSI S3.22-Specification of Hearing Aid ANSI S3.22-Specification of Hearing Aid Characteristics (2003 approved) Characteristics (2003 approved)

ANSI WG 81-Electroacoustic Evaluation ANSI WG 81-Electroacoustic Evaluation of Hearing Assistance Devices (Approval of Hearing Assistance Devices (Approval Pending)Pending)

AAA Task Force-Developing Guidelines for AAA Task Force-Developing Guidelines for Fitting and Evaluation of FM SystemsFitting and Evaluation of FM Systems

Assumptions in Fitting FM Assumptions in Fitting FM SystemsSystems

Properly Functioning Hearing AidProperly Functioning Hearing Aid Meets Specifications-ANSI S3.22Meets Specifications-ANSI S3.22

Properly Fit Hearing AidProperly Fit Hearing Aid Matched to the needs of the child or adult Matched to the needs of the child or adult

with hearing losswith hearing loss Properly Configured to Receive the Properly Configured to Receive the

FM SignalFM Signal Contacts removed on Direct Audio Input Contacts removed on Direct Audio Input

ConnectionsConnections Binaural Ear Level System is Optimal Binaural Ear Level System is Optimal

ArrangementArrangement Microphones at Ear LevelMicrophones at Ear Level

1. The auditory signal should be 1. The auditory signal should be as consistent as possibleas consistent as possible This facilitates learningThis facilitates learning Ideally this is achieved with Ideally this is achieved with

minimal changes of equipmentminimal changes of equipment

2. There are different signal input 2. There are different signal input levels to the hearing aid mic and levels to the hearing aid mic and to the FM mic in typical use to the FM mic in typical use situationssituations

Typical input to HA mic - 65 dB SPLTypical input to HA mic - 65 dB SPL Typical input to FM mic - 80 dB SPLTypical input to FM mic - 80 dB SPL

3. Think in terms of output rather than 3. Think in terms of output rather than gaingain Goal is to match SPL levels at the eardrum Goal is to match SPL levels at the eardrum

so that signal is consistent (exceptions will so that signal is consistent (exceptions will be discussed)be discussed)

Therefore, for same output, gains will differ Therefore, for same output, gains will differ because input levels are differentbecause input levels are different

EXAMPLE EXAMPLE using overall signal using overall signal

levelslevels Say that Mary hears best when level at Say that Mary hears best when level at

the eardrum is 100 dB SPLthe eardrum is 100 dB SPL For the HA FittingFor the HA Fitting

65 dB SPL input + 35 dB gain = 100 dB SPL65 dB SPL input + 35 dB gain = 100 dB SPL For the FM FittingFor the FM Fitting

80 dB SPL input + 20 dB gain = 100 dB SPL80 dB SPL input + 20 dB gain = 100 dB SPL

4. Use speech-weighted noise for 4. Use speech-weighted noise for frequency response and use tone sweep frequency response and use tone sweep for SSPL90for SSPL90

All of the energy in complex signal All of the energy in complex signal sums to an overall level, there is not sums to an overall level, there is not 70 dB at every frequency, but 70 dB 70 dB at every frequency, but 70 dB overall, therefore…..overall, therefore…..

The SPL at 1 kHz will be lower for 70 The SPL at 1 kHz will be lower for 70 dB speech weighted noise than for 70 dB speech weighted noise than for 70 dB sweep frequency tones. But….dB sweep frequency tones. But….

For a pure tone sweep, there IS 70 dB For a pure tone sweep, there IS 70 dB at every frequency at every frequency

5. Use FM settings first, then HA, to match 5. Use FM settings first, then HA, to match output for HA and HA+FM conditionsoutput for HA and HA+FM conditions Ideally want the child to put on Ideally want the child to put on

HA and not change settings when HA and not change settings when using FMusing FM

Need to check electroacoustically Need to check electroacoustically to determine if this is possibleto determine if this is possible

6. Optimize the testing6. Optimize the testing Try to do electroacoustic measures before Try to do electroacoustic measures before

patient arrivespatient arrives Perform real ear measures if possiblePerform real ear measures if possible When you have options to receive FM only When you have options to receive FM only

& FM+ENV, start first with the signal & FM+ENV, start first with the signal arrangement used most oftenarrangement used most often

EVALUATION OPTIONS EVALUATION OPTIONS forfor

FM SYSTEMSFM SYSTEMSA. Audio-Visual ChecksA. Audio-Visual ChecksB. Electroacoustic MeasurementsB. Electroacoustic Measurements

Verifying PerformanceVerifying PerformanceMatching FM’s to HA’sMatching FM’s to HA’s

C. Real Ear EvaluationC. Real Ear EvaluationMatching FM’s to HA’s Matching FM’s to HA’s

D. Behavioral EvaluationD. Behavioral EvaluationSpeech RecognitionSpeech Recognition

NEW TERMINOLOGYNEW TERMINOLOGY While in a sea of strips from the test While in a sea of strips from the test

box… it occurred to me that we needed box… it occurred to me that we needed new termsnew terms

Start Simple….First LetterStart Simple….First Letter E for Electroacoustic Measures E for Electroacoustic Measures

R for Real ear Measures R for Real ear Measures Then…Then…

HA for Hearing aid HA for Hearing aid FM for FM system in FM modeFM for FM system in FM mode

There are four basic There are four basic evaluation steps!evaluation steps!

1) HA - 65 dB SPL complex signal1) HA - 65 dB SPL complex signal

2) HA & FM - 80 dB SPL complex signal2) HA & FM - 80 dB SPL complex signal

3) HA – 90 dB pure tone signal3) HA – 90 dB pure tone signal

4) HA & FM – 90 dB pure tone signal4) HA & FM – 90 dB pure tone signal

EHA65

EFM/HA80

EHA90

EFM/HA90

SIMPLIST CASESIMPLIST CASEMILD TO MODERATE HEARING MILD TO MODERATE HEARING

LOSSLOSS

Gain is40 dB forHA

Gain is25 dB forFM

ENV signal10 dB belowFM and stillAudible

AuditoryArea

AmplifiedSpeech

UnamplifiedHA Mic

ENV MIC FM MIC FM+ENV MIC

dB

SP

L

0

100

Speech Input toFM Mic

MORE DIFFICULT CASEMORE DIFFICULT CASESEVERE TO PROFOUND SEVERE TO PROFOUND

HEARING LOSSHEARING LOSS

Gain is60 dB forHA due to Feedback

AuditoryArea

AmplifiedSpeech

Unamplified Speech Input toHA Mic

dB

SP

L

0

100

ENV MIC

MORE DIFFICULT CASEMORE DIFFICULT CASESEVERE TO PROFOUND SEVERE TO PROFOUND


Gain is60 dB forHA due toFeedback

Gain is45 dB forFM

ENV signal10 dB belowFM and NOTAudible

AmplifiedSpeech

Unamplified Speech Input toHA Mic FM Mic

AuditoryArea

dB

SP

L

0

100


MORE DIFFICULT CASEMORE DIFFICULT CASE SEVERE TO PROFOUND SEVERE TO PROFOUND

HEARING LOSSHEARING LOSSCharlieCharlie

So in this case, we want to amplify So in this case, we want to amplify the FM signal to a HIGHER intensity the FM signal to a HIGHER intensity than that achieved with the Hearing than that achieved with the Hearing AidAid

Electroacoustic Measurements

MORE DIFFICULT CASEMORE DIFFICULT CASE SEVERE TO PROFOUND SEVERE TO PROFOUND


Gain is60 dB forHA due toFeedback

Gain is60 dB forFM

ENV signal10 dB belowFM and NOWIS Audible

AuditoryArea

AmplifiedSpeech

Unamplified Speech Input toHA Mic FM Mic

dB

SP

L

0

100


Let’s Consider ….Let’s Consider ….

Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs

Preliminary SetupPreliminary Setup1. Set HA to User Settings

2. Set Test Equip for Complex Signal

3. Set Test Equip to display OUTPUT,

not gain

4. Go into Multicurve FunctionElectroacoustic Measurements

Set up for testing HA Set up for testing HA alonealone


BillieBillie

Change setting to Curve 1-Put HA Change setting to Curve 1-Put HA in test boxin test box

Curve 1. Test HA alone with 65 dB SPL Curve 1. Test HA alone with 65 dB SPL complex inputcomplex input


Set up for testing HA & Set up for testing HA & FMFM


BillieBillie

Change setting to Curve 2-Put Change setting to Curve 2-Put FM Transmitter in test box, FM Transmitter in test box, Attach FM Receiver Boot to HAAttach FM Receiver Boot to HA

Curve 2. Test HA&FM system (set to Curve 2. Test HA&FM system (set to FM only) with 80 dB SPL complex FM only) with 80 dB SPL complex inputinput



BillieBillie

Compare Curves 1 and 2 : EHA65 and Compare Curves 1 and 2 : EHA65 and EFM/HA80EFM/HA80

Adjust volume if necessary to match Adjust volume if necessary to match HA alone output, HA alone output,

If a programmable hearing aid , make If a programmable hearing aid , make and new program and refer to that as and new program and refer to that as “FM Program”“FM Program”



Checking Maximum Output- Checking Maximum Output- BillieBillie

Change setting to Curve 3-Put HA in Test Change setting to Curve 3-Put HA in Test BoxBox

Curve 3. Test HA alone with 90 dB SPL pure-Curve 3. Test HA alone with 90 dB SPL pure-tone sweep inputtone sweep input



Change setting to Curve 4-Put Change setting to Curve 4-Put FM Transmitter in test box, HA FM Transmitter in test box, HA with FM Receiver Boot and 2cc with FM Receiver Boot and 2cc coupler outsidecoupler outside

Curve 4. Test HA&FM system (set to Curve 4. Test HA&FM system (set to FM only) with 90 dB SPL pure-FM only) with 90 dB SPL pure-tone sweep inputtone sweep input

Match Max Output- Match Max Output- BillieBillie

Compare Curves 3 and 4, EHA90 Compare Curves 3 and 4, EHA90 and EFM/HA90and EFM/HA90

Adjust max output if necessary in Adjust max output if necessary in the “FM Program”, to match HA the “FM Program”, to match HA outputoutput


SUMMARY

These curves areclosely aligned except for the high frequenciesat the typical Input levels (1&2).

Additional highfrequency info. Isoften desirable.

Goals for VerficationGoals for Verfication

FM Advantage of about 10 dBFM Advantage of about 10 dB EFM/HA80 minus EHA65EFM/HA80 minus EHA65

FM Transparency of about 0 dBFM Transparency of about 0 dB EFM/HA90 minus EHA90EFM/HA90 minus EHA90

Real Ear MeasurementsReal Ear Measurements

Same principles re: matching output applySame principles re: matching output apply

Main difference is to place FM mic as close Main difference is to place FM mic as close to reference mic as possibleto reference mic as possible

Curves: RHA65, RFMHA80, RHA90, Curves: RHA65, RFMHA80, RHA90, RFMHA90RFMHA90

Real Ear Measurements

Set up for Leveling

Set up for testing HA alone

Set up for testing HA & FM

EVALUATION OPTIONSEVALUATION OPTIONS

A. Audio-Visual ChecksA. Audio-Visual ChecksB. Electroacoustic MeasurementsB. Electroacoustic Measurements

Verifying PerformanceVerifying PerformanceMatching FM’s to HA’sMatching FM’s to HA’s

C. Real Ear EvaluationC. Real Ear EvaluationMatching FM’s to HA’s Matching FM’s to HA’s

D. Behavioral EvaluationD. Behavioral EvaluationSpeech RecognitionSpeech Recognition

There are two main reasons why it is There are two main reasons why it is not advisable to do threshold testing not advisable to do threshold testing with the FM system.with the FM system.

The first one stems from the The first one stems from the suggestionsuggestionto place the FM mic 6 inches from theto place the FM mic 6 inches from theloudspeaker and place the child loudspeaker and place the child outsideoutsidethe booth….. the booth…..

Behavioral Measurements


1) There is too much variability in 1) There is too much variability in vertical and horizontal dimensions vertical and horizontal dimensions

which may result in variability in which may result in variability in the signal levels arriving at the FM the signal levels arriving at the FM mic.mic.



Behavioral Measurements 2) In addition, the FM systems may operate differently for low level signals than for higher level ones like speech because of compression.

THEREFORE…..Threshold testing with the FM system is not recommended!Rather……….


Speech Recognition Speech Recognition TestingTesting

Hearing Aid aloneHearing Aid alone FM SystemFM System

FM OnlyFM Only FM+ENV ModeFM+ENV Mode

Test each arrangement in Quiet Test each arrangement in Quiet and in Background noise if time and in Background noise if time permitspermits



Select appropriate test with multiple Select appropriate test with multiple listslists

Set FM and HA controls to user settingsSet FM and HA controls to user settings Place FM mic on examiner but turned Place FM mic on examiner but turned

offoff Place HA and FM receiver on PatientPlace HA and FM receiver on Patient Seat Patient in soundbooth at 45 Seat Patient in soundbooth at 45

degrees azimuthdegrees azimuth


INTERPRETATIONINTERPRETATION

Relate Laboratory findings to Clinical Relate Laboratory findings to Clinical ApplicationsApplications

How do you determine if a score is significantly How do you determine if a score is significantly low?low?

Or Or significantly different from another score?significantly different from another score?

Thornton and Raffin (1978) determined Thornton and Raffin (1978) determined the degree to which a second speech the degree to which a second speech recognition score must vary from an recognition score must vary from an

initial score to be significantly differentinitial score to be significantly different

Critical differences for speech recognition Critical differences for speech recognition scores (Thornton and Raffin,1978) scores (Thornton and Raffin,1978)

Initial Initial 100100 5050 2525 1010

9090 81-9681-96 76-9876-98 72-10072-100 50-10050-100

8080 68-8968-89 64-9264-92 56-9656-96 40-10040-100

7070 57-8157-81 52-8652-86 48-9248-92 30-9030-90

6060 47-7347-73 42-7842-78 36-8436-84 20-9020-90

5050 37-6337-63 32-6832-68 28-7628-76 10-9010-90

4040 27-5327-53 22-5822-58 16-6416-64 10-8010-80

3030 19-4319-43 14-4814-48 12-5612-56 10-7010-70

2020 11-3211-32 8-368-36 4-444-44 0-600-60

Disproportionately Low Disproportionately Low Scores?Scores?

Data for these comparisons were based Data for these comparisons were based on the 95% confidence limits of the PB on the 95% confidence limits of the PB Max for NU6 word lists from a sample of Max for NU6 word lists from a sample of 407 ears with a wide range of pure-tone 407 ears with a wide range of pure-tone averages (500, 1000 and 2000 Hz) averages (500, 1000 and 2000 Hz) (Dubno et al. 1995). (Dubno et al. 1995).

SPSPeech eech RRecognition ecognition INTINTerpretationerpretation

SPRINTSPRINT Chart Chart May be used: May be used: 1) to compare two speech recognition 1) to compare two speech recognition

scores or scores or 2) to compare PBmax score on NU6 lists 2) to compare PBmax score on NU6 lists

to to normative datanormative data

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 960 04 48 8 S

12 12 e16 16 c20 20 o24 24 n28 28 d

P 32 32T 36 36 PA 40 40 e

44 44 rd 48 48 cB 52 52 eH 56 56 nL 60 60 t

64 6468 68 S72 72 c76 76 o80 80 r84 84 e88 8892 9296 96

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96First Percent Correct Score

SPRINT Chart for 25-Word NU6 Lists

SPRINT Chart for 50-Word NU6 Lists0 10 20 30 40 50 60 70 80 90

0 0

10 10

20 20

S30 30 e

cond

P 40 40T PA e

rd cB 50 50 eH nL t

S60 60 c

ore

70 70

80 80

90 90

0 10 20 30 40 50 60 70 80 90

First Percent Correct Score

Speech recognition scores are Speech recognition scores are often interpreted based on some often interpreted based on some personal internal norms because personal internal norms because validated normative information is validated normative information is not conveniently available.not conveniently available.

Speech Recognition TestingSpeech Recognition TestingASHA GuidelinesASHA Guidelines

Test ConditionsTest Conditions HA-Quiet (Speech at 55 dB HL)HA-Quiet (Speech at 55 dB HL) HA-Noise (Add Speech Noise at 50 dBHL)HA-Noise (Add Speech Noise at 50 dBHL) HA&FM-Noise (Keep levels, Turn on FM HA&FM-Noise (Keep levels, Turn on FM

Mic)Mic) HA&FM-Quiet (Keep levels, Turn off HA&FM-Quiet (Keep levels, Turn off

noise)noise)



Sample ScoresSample Scores HA-Quiet HA-Quiet 80%80% HA-Noise HA-Noise 50%50% HA+FM-NoiseHA+FM-Noise 85%85%

If score decreases significantly, then FM gain too lowIf score decreases significantly, then FM gain too low HA+FM-QuietHA+FM-Quiet 80%80%

If score increases significantly, then FM gain too lowIf score increases significantly, then FM gain too low


You thought EHA65, You thought EHA65, EFM/HA90, EHAFM65, EFM/HA90, EHAFM65,

EFMHA80 were too Much!EFMHA80 were too Much! Hearing Aid AloneHearing Aid Alone

BHA55BHA55 BHA55/50BHA55/50

Hearing Aid + FM SystemHearing Aid + FM System BFM/HA55/50BFM/HA55/50 BFM/HA55BFM/HA55

Behavioral FM VerificationBehavioral FM VerificationCase IllustrationCase Illustration

Third Grader who resisted wearing FM Third Grader who resisted wearing FM system.system.

Testing done to show him benefits.Testing done to show him benefits. Hearing Aid AloneHearing Aid Alone

BHA55 BHA55 90%90% BHA55/50BHA55/50 60%60%

Hearing Aid with FMHearing Aid with FM BFM/HA55/50 (unlit FM)BFM/HA55/50 (unlit FM) 80%80% BFM/HA55/50 (bilat FM)BFM/HA55/50 (bilat FM) 90%90% BFM/HA55BFM/HA55 100%100%

Getting Desired ResultsGetting Desired Results

If the desired FM Advantage and FM If the desired FM Advantage and FM Transparency are not obtained, Transparency are not obtained, adjustments may be necessary to adjustments may be necessary to Hearing Aid/FM settings viaHearing Aid/FM settings via Manual adjustments-screwdrivers and Manual adjustments-screwdrivers and

trimpotstrimpots Programmable adjustments-software, Noah,Programmable adjustments-software, Noah,

TOASTER?TOASTER?

WATCH WHAT YOU SAY!!!WATCH WHAT YOU SAY!!!

SUMMARYSUMMARY

Goal of Fitting FM is to allow improved Goal of Fitting FM is to allow improved signal-to-noise ratio so that signal from signal-to-noise ratio so that signal from the FM transmitter is higher intensity the FM transmitter is higher intensity than background noisethan background noise

Electroacoustic Verification is Electroacoustic Verification is necessary to determine optimal signal necessary to determine optimal signal to noise ratioto noise ratio

Behavioral Verification with FM/HA Behavioral Verification with FM/HA combination useful for Counseling and combination useful for Counseling and Motivating StudentMotivating Student

fitting and evaluation of fm systems for ha users

Documents

db spl input

db spl slide

db gain

db spl typical input

spl levels

db sweep frequency tones

fm fitting

db speech weighted noise