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 Percentage Use
100 90 80 70 60 50 40 30 20 10 0 1994 1996 1998 2000
Years
2002 2004 2006 Analog non-prog Analog prog Digital 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% of all BTE’s sold in first half of 2006
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.
Phase Canceller
Digital Feedback Reduction Properties
Active Passive Notch Filter
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 method REUR – REAR = REIG • • Does this verify audibility has been delivered?
Does this demonstrate “improvement” with open-fittings?
Audibility method REAR 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
35.0
30.0
Oh good, it doesn’t matter which I use!
25.0
20.0
15.0
10.0
5.0
GAIN (dB) 0.0
100.0
1000.0
SPEECH GAIN TONE GAIN 10000.0
Output for speech is much less than output for pure tones
.
OUTPUT FOR 70 dB SPEECH & 70 dB TONE. K-AMP. MODERATE LOSS 110.0
105.0
100.0
95.0
90.0
85.0
80.0
Maybe you should just listen to tones.
75.0
70.0
65.0
OUTPUT (dB SPL) 60.0
100.0
1000.0
70 dB SPEECH 70 dB TONE
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
Understanding an SPLogram The Unaided SPLogram 1) Recruitment Accommodation Maximum output targets
Loud speech
Avg. speech
Soft speech
Threshold (dB SPL TM) Normal hearing
Example of Open Fit 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
2) Directional Verification
Laboratory Specification of Directionality
Polar Plots 300 315 330 345 360 0 0 -5 -10 -15 285 -20 270 255 240 225 210 195 15 30 45 60 75 90 105 180 165 150 135 120
Conventional Directional Microphone Test (Polar Plot Measurement) Sound Field Speaker 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)
Main Speaker
Concept Behind Directional Box Test
Secondary Speaker
2) Directional Verification
Clinical Verification of Directional Performance
B) Verifit REM Directional Verification Test selection Hearing Instrument Test Linear AGC Directional Distortion Input/Gain Multicurve Telecoil Manual control Calibration Real-Ear Measurement Speechmap Insertion gain Directional Manual control Calibration
2) Directional Verification
Directionality Test (REM)
Rear Facing Auxiliary Speaker Subject Verifit System In REM Directional Mode Aided Ear With Probe Tube Positioned
On-Ear Directional Test Result
REAR to Front Signal REAR to Back Signal
Viewport Screen View Facilitates Results Comparison
Example of Complete Box test 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 open fit 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