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
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 targets
Gain reduction for soft inputs: inexperienced user compared to most experienced user
Moderate sloping hearing loss
0
-2
Reduction in gain (dB)
-4
-6
HA 1
HA 2
HA 3
-8
-10
-12
-14
-16
100
1000
Frequency (Hz)
10000
Effect of experience level on targets
Gain reduction for soft inputs: inexperienced user compared to most experienced user
Flat severe loss
0
-2
Reduction in gain (dB)
-4
-6
HA 1
HA 2
HA 3
-8
-10
-12
-14
-16
100
1000
Frequency (Hz)
10000
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.
Top 10 reasons why clinicians do not run real ear
10.) Unclear on test result interpretation or how to
convey results to patients/Think digital cant be
verified by real ear
9.)
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 ear
6.)
Measures do not = more sales
5.)
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
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
Directional Microphone Noise
2-mic directionality with low frequency roll off
Traditional L/f compensation
+ Good Audibility
- High Noise
+ Low Noise
- Reduced Audibility
Hz
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
Four approaches to reducing noise
2
2
0
-2
RANDOM
BABBLE
0
-6
High versus OFF
(output change)
ON versus OFF
(output change)
-4
-8
-10
-12
-2
-4
-6
-14
-16
random-85dB
babble-85dB
-18
-8
-20
-10
125
250
500
1000
2000
4000
8000
125
250
500
Frequency(Hz)
1000
2000
4000
8000
Frequency(Hz)
2
10
0
DIFFERENCE (dB,1/3octave)
0
ON versus OFF
(output change)
-2
-4
-6
-8
85dB random
85dB babble
-10
-20
85dB RANDOM
85dB BABBLE
-30
-10
125
250
500
1000
2000
4000
8000
-40
125
250
500
1000
Frequency(Hz)
Frequency(Hz)
2000
4000
8000
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