fitting and evaluation of fm systems for ha users
TRANSCRIPT
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
HEARING LOSSHEARING LOSS
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
ENV MIC FM MIC FM+ENV MIC
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
HEARING LOSSHEARING LOSS
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
ENV MIC FM MIC FM+ENV MIC
MORE DIFFICULT CASEMORE DIFFICULT CASE SEVERE TO PROFOUND SEVERE TO PROFOUND
HEARING LOSSHEARING LOSS
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
ENV MIC FM MIC FM+ENV MIC
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
Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs
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
Electroacoustic Measurements
Set up for testing HA & Set up for testing HA & FMFM
Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs
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
Electroacoustic Measurements
Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs
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”
Electroacoustic Measurements
Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs
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
Electroacoustic Measurements
Steps to Verify HA and FM Steps to Verify HA and FM OutputsOutputs
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
Electroacoustic Measurements
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
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
Behavioral Measurements
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……….
Behavioral Measurements
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
Behavioral Measurements
Speech Recognition Speech Recognition TestingTesting
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
Behavioral Measurements
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)
Behavioral Measurements
Speech Recognition Speech Recognition TestingTesting
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
Behavioral Measurements
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