Practical Advice That Will Improve Your Hearing Aid Fittings

Laurel Christensen, Ph.D.

Chief Audiology OfficerGN ReSound Group

Adjunct ProfessorRush University, Chicago, IL

Northwestern University, Evanston, IL

What is being set for you when you press Autofit?

Gain Output Directional Settings

– Beam Width– Bass Boost

Noise Reduction Settings Feedback Suppression Settings Expansion Wind Noise Reduction Settings Memory Settings Steering Attack and Release Times

ReSound Auto Fit

Phonak

Starkey – Quick Fit

Gain/Output

Settings for first time, comfort, experienced linear, experienced non linear have a major effect on the gain of the hearing aid.

Rationale for acclimatization levels

Experience with amplification affects acceptance

Initially acceptable gain may be suboptimal for speech understanding

First fit was never meant to be “last fit”

Comfort User

Experience – Non Linear

Phonak – First Time User

Phonak – Long Term Users

Siemens – Level 1

Siemens – Level 4

Oticon – First Time User

Oticon - Experienced

Effect of experience level on targetsGain reduction for soft inputs: inexperienced user compared to most experienced user

Moderate sloping hearing loss

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Effect of experience level on targets

Gain reduction for soft inputs: inexperienced user compared to most experienced userFlat severe loss

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Effect of Experience Level Setting:First Fit Settings Two Hearing Aids – same audiogram

Mild sloping to moderately severe

HL

2cc coupler output with 65 dB SPL ISTS (international speech test signal)

Effect of Experience Level Setting:Experienced settings two hearing aids – same audiogram

Mild sloping to moderately severe

HL

2cc coupler output with 65 dB SPL ISTS (international speech test signal)

Audibility

Targets on the screen are not always what is actually in the ear.

One study says less than 12% of targets on the screen matched what was in the ear. (Aarts and Caffee, 2005)

A more recent study – Moore et al., 2008 showed similar results – that is what is on the screen usually isn’t what is in the ear.

10.) Unclear on test result interpretation or how to convey results to patients/Think digital cant

be verified by real ear9.) Not knowing when to verify 8.)  Perceptions that the measurement/probe

placement may be uncomfortable for patients 7.)  Changing technology (open fits, digitals, etc.)

negate the use of real ear6.)  Measures do not = more sales5.)  Can't bill for specific procedure 4.) Lack of confidence in procedures 3.) Do not own up-to-date equipment 2.) Who cares what the verification measure says

if patient is happy 1.) Time

Top 10 reasons why clinicians do not run real ear

Gain Verification

REIG is the gold standard Compare measured values to predicted gain

values Ensures optimal performance of the

instrument Does little to convey a message to patients

regarding how the instruments will help them

REUG

REIG

Speech Mapping

Today – Many system available and they go far beyond REIG

Speech Mapping

Provides information regarding targets for aided listening

Uses output rather than gain– Includes interactions from various algos

“real world” test signals can provide a more personal fitting technique– Spouse’s voice– Environmental sounds (paper rustling etc)

Display of results provides a useful talking point for counseling

Goals of Level Dependent Amplification

Soft Sounds should be audible Moderate sounds should be comfortable Loud sounds should be loud but not

intolerable Test signals can be presented at levels

comparable to “soft” “medium” and “loud” Provides real-time analysis of hearing aid

performance with features activated or deactivated as desired

Verification using the audibility area

To verify soft speech is audible– Deliver babble stimulus with VC set to low (50 to 55dB SPL)– Response curve should be at the lower level of the

audibility area To verify moderate speech is comfortable

– Deliver babble stimulus with VC set to the middle (65 to 70dB SPL)

– Response curve should be covering the audibility area To verify loud sounds are tolerable

– Deliver airplane stimulus with VC set to middle (~90 dB SPL)

– FFT peaks should not exceed the UCL values

Speech Mapping-Aurical VSM

10 dB threshold Speech Banana

Customized Speech banana

Speech Mapping-Aurical VSM

85 dB

53 dB

67 dB

Speech Mapping

Digital Feedback Suppression

Demonstrates how DFS can reduce feedback while not notching out the frequency response

Also demonstrates the amount of headroom that can be gained through the use of DFS technology

Enable probe mic but do not use any stimulus

Turn off all algos Increase gain to the point of

feedback measure output Turn on DFS measure output Turn up gain if headroom

demonstration is desired

Digital Feedback Suppression

Dynamic Feedback Measurement

Directionality

Incorporates 2 or more microphones into the hearing instrument in order to determine the direction of the signal of interest– Typically monitors the time difference between

microphones In directionality mode, the hearing instrument will reduce gain

of signals presented from behind and/or to the sides of the individual

3% of time hearing instruments are wired backwards – Verifying directionality before fitting will catch this problem

Directionality and low freq equalization

2-mic directionality with low frequency roll off

Traditional L/f compensation

Hz

+ Low Noise- Reduced Audibility

+ Good Audibility- High Noise

Directional Microphone Noise

Directional Test Setup

Verify with a single noise signal presented behind the patient– Turn chair to 180˚

Present ANSI speech noise or babble at 65 dB SPL– Present stimulus with directionality ON– Present stimulus with directionality OFF

Curve obtained with directionality ON will have a smaller amplitude than the curve obtained with directionality OFF

Directional Test Setup

Directionality

Noise Reduction

Demonstrates how noisy signal levels are reduced through the use of this algorithm

Use continuous noise– White noise– Test with all other algorithms disabled– Obtain 2 measurements

• 1st with noise reduction disabled• 2nd with noise reduction set to strong

Patient may hear as well as see the impact of this algorithm

Frequency(Hz)

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Four approaches to reducing noise

Noise Reduction

Wind Noise Reduction

Hearing aid wind noise is caused by turbulent air flow around the microphone.

This turbulence will result in movement of the microphone diaphragm that will in turn be amplified

This amplification can overload the hearing aid resulting in wind noise

The amount of wind is dependent on wind speed An effective demonstration can be performed in office

using a motorized fan The effect of the wind generated by the fan can be

measured using a probe microphone system Compare the measurements with and without WNR

activated Can also be used to demonstrate how microphone

placement effects wind noise

Wind Noise Reduction Algorithm

Conclusions

Auto Fit is only a place to start and shouldn’t be for many patients an ending point.

Acceptable Noise Level

Acceptable noise level (ANL) is defined as the maximum level of background noise that an individual is willing to accept while listening to speech.

The ANL measure assumes that speech understanding in noise may not be as important as is the willingness to listen in the presence of noise.

ANL

The ANL is established by adjusting a recorded story to the listener’s most comfortable listening level (MCL).

Then the background noise is added and adjusted to the highest acceptable background noise level (BNL) while the listener is following the words of the story.

The ANL, in decibels, is calculated by subtracting the BNL from the MCL.

What Can It Tell You?

Predictor of hearing aid success People who accept background noise have smaller

ANLs and tend to be "good" users of hearing aids People who cannot accept background noise have

larger ANLs and may only use hearing aids occasionally or reject them altogether

Useful for counseling and setting realistic expectations

Mueller et al., 2006 reported reduced ANLs when digital noise reduction was activated.

Freyaldenhoven et al., 2005 showed ANLs can be improved with the use of directional hearing aid technology

Hearing Aid Outcomes

Issues in Evaluating the Effectiveness of Hearing Aids in the Elderly: What to Measure and When – Larry Humes, Ph.D.– Seminars in Hearing, 2001

• In clinical practice if one can identify those that are not benefiting from their hearing aids, then it might be possible to intervene with more counseling, rehabilitation, or different technology.

7 Independent Dimensions of Hearing Aid Outcome

Subjective benefit and Satisfaction– Hearing Aid Performance Inventory (HAPI)– Hearing Aid Satisfaction Survey (HASS)– Satisfaction with Amplification in Daily Life (SADL)

Aided performance– Connected Speech Test (CST)

Hearing Aid Use– Use Diary

Objective Benefit– Aided-Unaided CST scores

High-intensity Speech in Noise– CST score at 80 dB SPL, 0 dB SNR– Aided-Unaided CST-80 score

Handicap Reduction– Aided-Unaided HHIE (Hearing Handicap Inventory for the Elderly)

score Judged Sound Quality

– JSQ ratings for speech and music stimuli

THANK YOU