Fitting and Evaluation of FM Systems for HA Users

Guidelines for Fitting and Evaluation ANSI S3.22-Specification of Hearing Aid Characteristics (2003 approved) ANSI WG 81-Electroacoustic Evaluation of Hearing Assistance Devices (Approval Pending) AAA Task Force-Developing Guidelines for Fitting and Evaluation of FM Systems

Assumptions in Fitting FM Systems Properly Functioning Hearing Aid Properly Functioning Hearing Aid Meets Specifications-ANSI S3.22 Meets Specifications-ANSI S3.22 Properly Fit Hearing Aid Properly Fit Hearing Aid Matched to the needs of the child or adult with hearing loss Matched to the needs of the child or adult with hearing loss Properly Configured to Receive the FM Signal Properly Configured to Receive the FM Signal Contacts removed on Direct Audio Input Connections Contacts removed on Direct Audio Input Connections Binaural Ear Level System is Optimal Arrangement Binaural Ear Level System is Optimal Arrangement Microphones at Ear Level Microphones at Ear Level

1. The auditory signal should be as consistent as possible This facilitates learning This facilitates learning Ideally this is achieved with minimal changes of equipment Ideally this is achieved with minimal changes of equipment

2. There are different signal input levels to the hearing aid mic and to the FM mic in typical use situations Typical input to HA mic - 65 dB SPL Typical input to HA mic - 65 dB SPL Typical input to FM mic - 80 dB SPL Typical input to FM mic - 80 dB SPL

3. Think in terms of output rather than gain Goal is to match SPL levels at the eardrum so that signal is consistent (exceptions will be discussed) Goal is to match SPL levels at the eardrum so that signal is consistent (exceptions will be discussed) Therefore, for same output, gains will differ because input levels are different Therefore, for same output, gains will differ because input levels are different

EXAMPLE using overall signal levels Say that Mary hears best when level at the eardrum is 100 dB SPL Say that Mary hears best when level at the eardrum is 100 dB SPL For the HA Fitting For the HA Fitting 65 dB SPL input + 35 dB gain = 100 dB SPL 65 dB SPL input + 35 dB gain = 100 dB SPL For the FM Fitting For the FM Fitting 80 dB SPL input + 20 dB gain = 100 dB SPL 80 dB SPL input + 20 dB gain = 100 dB SPL

4. Use speech-weighted noise for frequency response and use tone sweep for SSPL90 All of the energy in complex signal sums to an overall level, there is not 70 dB at every frequency, but 70 dB overall, therefore….. All of the energy in complex signal sums to an overall level, there is not 70 dB at every frequency, but 70 dB overall, therefore…..

The SPL at 1 kHz will be lower for 70 dB speech weighted noise than for 70 dB sweep frequency tones. But…. The SPL at 1 kHz will be lower for 70 dB speech weighted noise than for 70 dB sweep frequency tones. But…. For a pure tone sweep, there IS 70 dB at every frequency For a pure tone sweep, there IS 70 dB at every frequency

5. Use FM settings first, then HA, to match output for HA and HA+FM conditions Ideally want the child to put on HA and not change settings when using FM Ideally want the child to put on HA and not change settings when using FM Need to check electroacoustically to determine if this is possible Need to check electroacoustically to determine if this is possible

6. Optimize the testing Try to do electroacoustic measures before patient arrives Try to do electroacoustic measures before patient arrives Perform real ear measures if possible Perform real ear measures if possible When you have options to receive FM only & FM+ENV, start first with the signal arrangement used most often When you have options to receive FM only & FM+ENV, start first with the signal arrangement used most often

EVALUATION OPTIONS for FM SYSTEMS A. Audio-Visual Checks B. Electroacoustic Measurements Verifying Performance Matching FM’s to HA’s C. Real Ear Evaluation Matching FM’s to HA’s D. Behavioral Evaluation Speech Recognition

NEW TERMINOLOGY While in a sea of strips from the test box… it occurred to me that we needed new terms While in a sea of strips from the test box… it occurred to me that we needed new terms Start Simple….First Letter Start Simple….First Letter E for Electroacoustic Measures R for Real ear Measures E for Electroacoustic Measures R for Real ear Measures Then… Then… HA for Hearing aid HA for Hearing aid FM for FM system in FM mode FM for FM system in FM mode

There are four basic evaluation steps! 1) HA - 65 dB SPL complex signal 2) HA & FM - 80 dB SPL complex signal 3) HA – 90 dB pure tone signal 4) HA & FM – 90 dB pure tone signal EHA65 EFM/HA80 EHA90 EFM/HA90

SIMPLIST CASE MILD TO MODERATE HEARING LOSS Gain is 40 dB for HA Gain is 25 dB for FM ENV signal 10 dB below FM and still Audible Auditory Area Amplified Speech Unamplified HA Mic ENV MICFM MICFM+ENV MIC dB SPL Speech Input to FM Mic

MORE DIFFICULT CASE SEVERE TO PROFOUND HEARING LOSS Gain is 60 dB for HA due to Feedback Auditory Area Amplified Speech Unamplified Speech Input to HA Mic dB SPL ENV MIC

MORE DIFFICULT CASE SEVERE TO PROFOUND HEARING LOSS Gain is 60 dB for HA due to Feedback Gain is 45 dB for FM ENV signal 10 dB below FM and NOT Audible Amplified Speech Unamplified Speech Input to HA Mic FM Mic Auditory Area dB SPL ENV MICFM MICFM+ENV MIC

MORE DIFFICULT CASE SEVERE TO PROFOUND HEARING LOSS Charlie So in this case, we want to amplify the FM signal to a HIGHER intensity than that achieved with the Hearing Aid So in this case, we want to amplify the FM signal to a HIGHER intensity than that achieved with the Hearing Aid Electroacoustic Measurements

MORE DIFFICULT CASE SEVERE TO PROFOUND HEARING LOSS Gain is 60 dB for HA due to Feedback Gain is 60 dB for FM ENV signal 10 dB below FM and NOW IS Audible Auditory Area Amplified Speech Unamplified Speech Input to HA Mic FM Mic dB SPL ENV MICFM MICFM+ENV MIC

MORE DIFFICULT CASE SEVERE TO PROFOUND HEARING LOSS Gain is 60 dB for HA due to Feedback Gain is 60 dB for FM ENV signal 10 dB below FM and NOW IS Audible Auditory Area Amplified Speech Unamplified Speech Input to HA Mic FM Mic dB SPL ENV MICFM MICFM+ENV MIC

Let’s Consider ….

Steps to Verify HA and FM Outputs Preliminary Setup 1. 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 Function Electroacoustic Measurements

Set up for testing HA alone

Steps to Verify HA and FM Outputs Billie Change setting to Curve 1-Put HA in test box Curve 1. Test HA alone with 65 dB SPL complex input Electroacoustic Measurements

Set up for testing HA & FM

Steps to Verify HA and FM Outputs Billie Change setting to Curve 2-Put FM Transmitter in test box, Attach FM Receiver Boot to HA Curve 2. Test HA&FM system (set to FM only) with 80 dB SPL complex input Electroacoustic Measurements

Steps to Verify HA and FM Outputs Billie Compare Curves 1 and 2 : EHA65 and EFM/HA80 Compare Curves 1 and 2 : EHA65 and EFM/HA80 Adjust volume if necessary to match HA alone output, Adjust volume if necessary to match HA alone output, If a programmable hearing aid, make and new program and refer to that as “FM Program” If a programmable hearing aid, make and new program and refer to that as “FM Program” Electroacoustic Measurements

Steps to Verify HA and FM Outputs Checking Maximum Output- Billie Change setting to Curve 3-Put HA in Test Box Curve 3. Test HA alone with 90 dB SPL pure-tone sweep input Electroacoustic Measurements

Steps to Verify HA and FM Outputs Change setting to Curve 4-Put FM Transmitter in test box, HA with FM Receiver Boot and 2cc coupler outside Curve 4. Test HA&FM system (set to FM only) with 90 dB SPL pure-tone sweep input

Match Max Output- Billie Compare Curves 3 and 4, EHA90 and EFM/HA90 Compare Curves 3 and 4, EHA90 and EFM/HA90 Adjust max output if necessary in the “FM Program”, to match HA output Adjust max output if necessary in the “FM Program”, to match HA output Electroacoustic Measurements

SUMMARY These curves are closely aligned except for the high frequencies at the typical Input levels (1&2). Additional high frequency info. Is often desirable.

Goals for Verfication FM Advantage of about 10 dB FM Advantage of about 10 dB EFM/HA80 minus EHA65 EFM/HA80 minus EHA65 FM Transparency of about 0 dB FM Transparency of about 0 dB EFM/HA90 minus EHA90 EFM/HA90 minus EHA90

Real Ear Measurements Same principles re: matching output apply Same principles re: matching output apply Main difference is to place FM mic as close to reference mic as possible Main difference is to place FM mic as close to reference mic as possible Curves: RHA65, RFMHA80, RHA90, RFMHA90 Curves: RHA65, RFMHA80, RHA90, RFMHA90 Real Ear Measurements

Set up for Leveling

Set up for testing HA alone

Set up for testing HA & FM

EVALUATION OPTIONS A. Audio-Visual Checks B. Electroacoustic Measurements Verifying Performance Matching FM’s to HA’s C. Real Ear Evaluation Matching FM’s to HA’s D. Behavioral Evaluation Speech Recognition

There are two main reasons why it is not advisable to do threshold testing with the FM system. The first one stems from the suggestion to place the FM mic 6 inches from the loudspeaker and place the child outside the booth….. Behavioral Measurements

1) There is too much variability in vertical and horizontal dimensions which may result in variability in the signal levels arriving at the FM 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………. Behavioral Measurements

Speech Recognition Testing Hearing Aid alone Hearing Aid alone FM System FM System FM Only FM Only FM+ENV Mode FM+ENV Mode Test each arrangement in Quiet and in Background noise if time permits Test each arrangement in Quiet and in Background noise if time permits Behavioral Measurements

Speech Recognition Testing Select appropriate test with multiple lists Select appropriate test with multiple lists Set FM and HA controls to user settings Set FM and HA controls to user settings Place FM mic on examiner but turned off Place FM mic on examiner but turned off Place HA and FM receiver on Patient Place HA and FM receiver on Patient Seat Patient in soundbooth at 45 degrees azimuth Seat Patient in soundbooth at 45 degrees azimuth Behavioral Measurements

INTERPRETATION INTERPRETATION Relate Laboratory findings to Clinical Applications How do you determine if a score is significantly low? How do you determine if a score is significantly low? Or Or significantly different from another score? significantly different from another score?

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

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

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

SPeech Recognition INTerpretation SPRINT Chart May be used: May be used: 1) to compare two speech recognition scores or 1) to compare two speech recognition scores or 2) to compare PBmax score on NU6 lists to 2) to compare PBmax score on NU6 lists to normative data normative data

SPRINT Chart for 25-Word NU6 Lists

SPRINT Chart for 50-Word NU6 Lists

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

Speech Recognition Testing ASHA Guidelines Test Conditions Test 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 Mic) HA&FM-Noise (Keep levels, Turn on FM Mic) HA&FM-Quiet (Keep levels, Turn off noise) HA&FM-Quiet (Keep levels, Turn off noise) Behavioral Measurements

Speech Recognition Testing Sample Scores HA-Quiet 80% HA-Quiet 80% HA-Noise 50% HA-Noise 50% HA+FM-Noise85% HA+FM-Noise85% If score decreases significantly, then FM gain too low If score decreases significantly, then FM gain too low HA+FM-Quiet80% HA+FM-Quiet80% If score increases significantly, then FM gain too low If score increases significantly, then FM gain too low Behavioral Measurements

You thought EHA65, EFM/HA90, EHAFM65, EFMHA80 were too Much! Hearing Aid Alone Hearing Aid Alone BHA55 BHA55 BHA55/50 BHA55/50 Hearing Aid + FM System Hearing Aid + FM System BFM/HA55/50 BFM/HA55/50 BFM/HA55 BFM/HA55

Behavioral FM Verification Case Illustration Third Grader who resisted wearing FM system. Testing done to show him benefits. Hearing Aid Alone Hearing Aid Alone BHA55 90% BHA55 90% BHA55/5060% BHA55/5060% Hearing Aid with FM Hearing Aid with FM BFM/HA55/50 (unlit FM)80% BFM/HA55/50 (unlit FM)80% BFM/HA55/50 (bilat FM)90% BFM/HA55/50 (bilat FM)90% BFM/HA55100% BFM/HA55100%

Getting Desired Results If the desired FM Advantage and FM Transparency are not obtained, adjustments may be necessary to Hearing Aid/FM settings via If the desired FM Advantage and FM Transparency are not obtained, adjustments may be necessary to Hearing Aid/FM settings via Manual adjustments-screwdrivers and trimpots Manual adjustments-screwdrivers and trimpots Programmable adjustments-software, Noah, Programmable adjustments-software, Noah,TOASTER? WATCH WHAT YOU SAY!!!

SUMMARY Goal of Fitting FM is to allow improved signal- to-noise ratio so that signal from the FM transmitter is higher intensity than background noise Goal of Fitting FM is to allow improved signal- to-noise ratio so that signal from the FM transmitter is higher intensity than background noise Electroacoustic Verification is necessary to determine optimal signal to noise ratio Electroacoustic Verification is necessary to determine optimal signal to noise ratio Behavioral Verification with FM/HA combination useful for Counseling and Motivating Student Behavioral Verification with FM/HA combination useful for Counseling and Motivating Student