Practical Advice That Will Improve Your Hearing Aid Fittings Laurel Christensen, Ph.D. Chief Audiology Officer GN ReSound Group Adjunct Professor Rush University, Chicago, IL Northwestern University, Evanston, IL
Dec 17, 2015
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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0
100 1000 10000
Frequency (Hz)
Red
uct
ion
in g
ain
(d
B)
HA 1
HA 2
HA 3
Effect of experience level on targets
Gain reduction for soft inputs: inexperienced user compared to most experienced userFlat severe loss
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0
100 1000 10000
Frequency (Hz)
Red
uct
ion
in g
ain
(d
B)
HA 1
HA 2
HA 3
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)
125 250 500 1000 2000 4000 8000
ON
ve
rsus
OF
F(o
utpu
t ch
ange
)
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random-85dB babble-85dB
Frequency(Hz)
125 250 500 1000 2000 4000 8000
ON
ver
sus
OF
F(o
utpu
t ch
ange
)
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0
2
85dB random85dB babble
Frequency(Hz)
125 250 500 1000 2000 4000 8000
DIF
FE
RE
NC
E (
dB
,1/3
octa
ve)
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0
10
85dB RANDOM 85dB BABBLE
Frequency(Hz)
125 250 500 1000 2000 4000 8000
Hig
h v
ers
us
OF
F(o
utp
ut
cha
nge
)
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-8
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0
2
RANDOM BABBLE
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