Transcript 2007 CEU Theater Slides: Verifying Open Ear Fittings

AAA CEU Theater Program
Verifying Open-Ear Fittings
With Speech-Mapping
David J. Smriga, M.A.
Audiologist
Hearing Industry Consultant
Technology Utilization Rates
100
90
80
70
60
Percentage Use
50
Analog non-prog
40
Analog prog
30
Digital
20
10
0
1994
1996
1998
2000
2002
2004
2006
Years
Strom, Karl, “Rapid Product Changes Mark The New Mature Digital Market” Hearing Review
Vol. 13, No. 5, 2006 p.p.70-75
BTE Growth Spurt

After 20% or less
of the market in
the ’80’s and
’90’s, look at
BTE’s now:
26.4% in 2004
 32.6% in 2005
 42.00 in first
half of 2006

Fueling That
Growth


Directional microphones
Open fit hearing aids
 27%
2006
of all BTE’s sold in first half of
Why the Renaissance
in Open Fit
Popularity?




Minimal occlusion via a narrow
tube fitting (or large vented
earmold)
Digital feedback cancellation
Precise frequency response setting
Mini (or micro) BTE designs
 Open-fit

ITE design now available
Directional microphones with open
fit aids?
Minimal Occlusion
Lybarger S. Earmolds. In: Katz J, ed. Handbook of Clinical Audiology, 3rd edition. Baltimore: Williams and Wilkins; 1985: 885-910.
Digital Feedback
Reduction
Properties
Active
Phase
Canceller
Notch
Filter
Passive
Precise Frequency
Response/Compression
Setting

Digital hearing instruments offer
the most precise hearing
instrument performance setting:
 Multiple
bands
 Variable compression settings by
band
 Low
and multiple knee points
 Variable compression ratios

This makes digital hearing aids
dynamically interactive
Objective
Verification of
Open Fittings
Real Ear Basics
Real-ear loudspeakers
Probe Microphone Assemblies
Key Issues

Input stimulus
 Traditional
options
 Sweep
frequency pure tone
 Noise stimulus
 Speech
stimuli
 Activates
adaptive features
The output of a compression aid
depends on the nature of its input
signal
The output of a compression aid
depends on the nature of its input
signal
The output of a compression aid
depends on the nature of its input
signal
Key Issues

Insertion gain vs. audibility
 Traditional
 REUR
method
– REAR = REIG
• Does this verify audibility has been
delivered?
• Does this demonstrate “improvement”
with open-fittings?
 Audibility
 REAR
method
compared to audibility
threshold
45.0
For this compression hearing
aid...
Gain for speech @ Gain for tones
GAIN FOR 70 dB SPEECH & 70 dB TONE. K-AMP. MODERATE LOSS
40.0
Oh good,
it doesn’t matter
which I use!
35.0
30.0
25.0
20.0
15.0
10.0
5.0
SPEECH GAIN
0.0
TONE GAIN
GAIN (dB)
100.0
1000.0
10000.0
Output for speech is
much less than output for pure
tones.
110.0
OUTPUT FOR 70 dB SPEECH & 70 dB TONE. K-AMP. MODERATE LOSS
105.0
Maybe you
should just
listen to
tones.
100.0
95.0
90.0
85.0
80.0
75.0
70.0
65.0
60.0
70 dB SPEECH
OUTPUT (dB SPL)
100.0
70 dB TONE
1000.0
10000.0
Speech Is An Excellent
WDRC Measurement
Stimulus


It IS the most important input
signal that the patient will want to
hear well and comfortably
It interacts with multi-band
compressors in a more realistic
way than tones
 band
interactions across frequency
 changing intensity
dB SPL Eardrum reference
Sounds get louder as you go UP the scale
Understanding an SPLogram
The Unaided SPLogram
Maximum output targets
Loud speech
Avg. speech
Soft speech
Threshold (dB SPL TM)
Normal hearing
1) Recruitment
Accommodation
Example of OpenFit REAR Result
Aid’s contribution
Pink banana = REAR with aid OFF
Green banana = REAR with aid ON
The SII Score
An Open-Fit
Verification
Protocol




Measure REAR with instrument on
ear but turned off
Measure REAR with instrument on
ear and turned on
Adjust gain to maximize SII without
invoking feedback
Use the fitting screen as a
counseling tool
Can Directional
Microphones Work In
An Open Fit
Environment?
The Aided Frequency
Response That Reaches
The Ear
Two Omni-directional Mics
With Digital Processor
DSP
H. Dillon; NAL, CRC for CI and HAI
Measuring Directional
Microphones Using
Polar Plots
Laboratory
Specification of
Directionality
Polar Plots
0
345
360 0
330
15
-5
30
45
315
60
-10
300
75
-15
285
90
-20
270
105
255
120
240
135
225
210
2) Directional
Verification
150
195
180 165
Conventional Directional Microphone Test
(Polar Plot Measurement)
Sound Field Speaker
Anechoic Chamber
Pure Tone Frequency
Issues Associated with
Conventional Polar Plot
Testing



Polar plots are obtained in the
presence of a single pure tone
frequency
Polar plots do not measure in the
presence of multiple input
sources
Polar plots can not be obtained in
the presence of non-linear
(compression) amplification
A New Way of Measuring
Directional Microphone
Performance
Obtaining a Directional
Microphone Frequency Response
in the Presence of Multiple Input
Source Locations
Verifit Testing System Hardware
Main Signal
Source
Coupler Chamber
Secondary Signal
Source
Directional Frequency
Response Input
Stimulus
= Main input signal (512 pure tones 7.8Hz apart)
= Secondary input signal (512 pure tones 7.8 Hz apart)
Frequency (KHz)
Concept Behind
Directional Box Test
Main Speaker
Secondary Speaker
Clinical Verification of
Directional Performance
B) Verifit REM Directional Verification
Test selection
2) Directional
Verification
Hearing Instrument Test
Linear
AGC
Directional
Distortion
Input/Gain
Multicurve
Telecoil
Manual control
Calibration
Real-Ear Measurement
Speechmap
Insertion gain
Directional
Manual control
Calibration
Directionality Test (REM)
Rear Facing
Auxiliary
Speaker
Verifit System
In REM Directional
Mode
Subject
Aided Ear
With Probe
Tube Positioned
2) Directional
Verification
On-Ear Directional
Test Result
REAR to Front Signal
REAR to Back Signal
Viewport Screen View
Facilitates Results
Comparison
Example of Complete Boxtest Viewport Result
SRT-in-Noise
Improvement With Open
Fit Directional Mic
Fabry, D., “Facts vs. Myths: The ‘Skinny’ On Slim-Tube Open Fittings” Hearing Review, May, 2006
Conclusions

Modern open-fits facilitated by:
Digital control of feedback
 Digital control of non-linearity
 Digital improvement in directional
performance


Objective on-ear measurements of openfit products are possible

Key elements to accomplish this:
Speech input stimuli
 Measure eardrum SPL instead of gain


Objective measures of directional
performance are possible

Can confirm directional function in aided
area