Verifying open ear fittings with speech mapping
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Verifying Open-Ear Fittings With Speech-Mapping. AAA CEU Theater Program. David J. Smriga, M.A. Audiologist Hearing Industry Consultant. 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.

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Verifying Open-Ear Fittings With Speech-Mapping

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Verifying open ear fittings with speech mapping

Verifying Open-Ear Fittings With Speech-Mapping

AAA CEU Theater Program

David J. Smriga, M.A.

Audiologist

Hearing Industry Consultant


Verifying open ear fittings with speech mapping

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

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

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

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

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

Digital Feedback Reduction Properties

Passive

Active

Phase

Canceller

Notch

Filter


Precise frequency response compression setting

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

Objective Verification of Open Fittings


Real ear basics

Real Ear Basics

Real-ear loudspeakers

Probe Microphone Assemblies


Key issues

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 signal1

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 signal2

The output of a compression aid depends on the nature of its input signal


Key issues1

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


For this compression hearing aid gain for speech @ gain for tones

Oh good,

it doesn’t matter

which I use!

For this compression hearing aid...Gain for speech @Gain for tones


Output for speech is much less than output for pure tones

Maybe you

should just

listen to

tones.

Output for speech is much less than output for pure tones.


Speech is an excellent wdrc measurement stimulus

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

Loud speech

Avg. speech

Sounds get louder as you go UP the scale

Soft speech

Understanding an SPLogramThe Unaided SPLogram

Maximum output targets

dB SPL Eardrum reference

Threshold (dB SPL TM)

Normal hearing

1) Recruitment

Accommodation


Example of open fit rear result

Example of Open-Fit REAR Result

Aid’s contribution

Pink banana = REAR with aid OFF

Green banana = REAR with aid ON


The sii score

The SII Score


An open fit verification protocol

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

Can Directional Microphones Work In An Open Fit Environment?


The aided frequency response that reaches the ear

The Aided Frequency Response That Reaches The Ear


Two omni directional mics with digital processor

Two Omni-directional Mics With Digital Processor

DSP

H. Dillon; NAL, CRC for CI and HAI


Measuring directional microphones using polar plots

Measuring Directional Microphones Using Polar Plots


Laboratory specification of directionality

0

360

0

15

345

30

330

-5

45

315

60

-10

300

75

-15

285

90

-20

270

105

255

120

240

135

225

150

210

165

195

180

Laboratory Specification of Directionality

Polar Plots

2) Directional

Verification


Verifying open ear fittings with speech mapping

Conventional Directional Microphone Test

(Polar Plot Measurement)

Sound Field Speaker

Pure Tone Frequency

Anechoic Chamber


Issues associated with conventional polar plot testing

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


Verifying open ear fittings with speech mapping

Obtaining a Directional Microphone Frequency Response in the Presence of Multiple Input Source Locations

A New Way of Measuring Directional Microphone Performance


Verifying open ear fittings with speech mapping

Verifit Testing System Hardware

Coupler Chamber

Secondary Signal

Source

Main Signal

Source


Directional frequency response input stimulus

= Secondary input signal (512 pure tones 7.8 Hz apart)

Directional Frequency Response Input Stimulus

= Main input signal (512 pure tones 7.8Hz apart)

Frequency (KHz)


Verifying open ear fittings with speech mapping

Concept Behind Directional Box Test

Main Speaker

Secondary Speaker


Verifying open ear fittings with speech mapping

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

Directionality Test (REM)

Verifit System

In REM Directional

Mode

Rear Facing Auxiliary Speaker

Subject

Aided Ear

With Probe

Tube Positioned

2) Directional

Verification


On ear directional test result

On-Ear Directional Test Result

REAR to Front Signal

REAR to Back Signal


Viewport screen view facilitates results comparison

Viewport Screen View Facilitates Results Comparison


Example of complete box test viewport result

Example of Complete Box-test Viewport Result


Srt in noise improvement with open fit directional mic

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

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


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