2007 CEU Theater Slides: Verifying Open Ear Fittings

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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