a master hearing aid system for auditory tests of hearing impaired...

A master hearing aid system for auditory tests of hearing impaired people

Stefan Stenfelt

Background

7 JUNE 2017 2 Stefan Stenfelt

• Investigations with participants with normal hearing function and hearing impairments.

• Need to compensate for audibility.

• Own hearing aids are ecological, but impose problems with different settings and lack of controlled gain

The N200 study


N200 study, participants


Three groups 1. Hearing impaired using hearing aids (n=200) 2. Normal hearing participants matched to group 1 (n=200) 3. Hearing impaired not using hearing aids (approx 100)

Group 1

N200 study, tests.


Auditory tests • Pure tone thresholds, AC and BC • PB-words in quiet • DPOAE • Binaural TFS sensitivity (TFS-LF) • TEN HL • Spectro-Temporal Modulation

Cognitive tests • Phonological tests

• Semantic long-term memory

• Working memory

• Executive &inference-making functions

• General cognitive functioning

Outcome tests • HINT • Hagerman sentences • Samuelsson & Rönnberg sentences • Auditory inference-making test • Speech, Spatial and Qualities of hearing

(SSQ)

Hearing aid signal processing


The Hagerman sentence test was conducted with three different amplification and signal processing 1. Linear amplification (voice aligned compression rationale) 2. Wide dynamic range compression (2:1 compression, 10 ms attack

and 80 ms release time) 3. Linear amplification + non-ideal binary mask noise reduction

Two different noises were used,

1. Stationary speech-weighted noise

2. 4-talker babble

In total 6 conditions

Controlled hearing amplification


• Use hearing aids that are fitted to each individual

• Use a central hearing aid and provide the acoustic output to the participant (MOSAIC)

• Computer-based gain (MATLAB)

• Computer-based Master Hearing Aid System

Hearing aids fitted to individuals


Pros

- Real acoustic setting

- Wearable

- Binaural

Cons

- No control of prescription implementation (even if generic)

- Acoustics not controlled (influence from head, pinna etc)

- Reprogramming, handling

- Restricted parameter values

Central hearing aid


2cc coupler

Anechoic test-box

Amplifier

ER3 earphones

Pros

- Controlled acoustic input

- Easy programming

- No level problems

- Participant outside testroom

Cons

- No control of prescription implementation (even if generic)

- Restricted parameter values

- Noise

- Binaural problematic

Computer-based gain (MATLAB)


Pros

- Controlled acoustic output (calibrated)

- Controlled gain function

- Signal processing

- Simulated environment

- Participant outside testroom

Cons

- Multiple sources not possible

- Primarily pre-recorded stimulus

Computer-based Master Hearing Aid System


Pros

- Same as Computer-based gain system

- Real-time function

- Multiple sources

Cons

- Price!

- Non-wearable

Studies


Hearing aid Central hearing aid Matlab based MHA

Speech perception

Speech perception Real life

Speech perception Simulated environment

Hearing aid evaluation

Signal processing development/evaluation

N200, results: Factor analysis


Factor

SENSITIVITY

TEMPORAL

FINE STRUC

HE

AR

ING

PTA 0.91 0.05

TEN HL 0.06 0.16

DPOAE -0.29 0.03

TFS-LF -0.29 0.92

STM 0.10 0.48

PB words 0.37 0.34

COGNITION

CO

GN

ITIO

N Phonology 0.59

LT memory 0.53

WM 0.63

Executive func 0.92

General cog func 0.43

CONTEXT NO CONTEXT

OU

TC

OM

E HINT 0.87 0.32

Hagerman 0.25 0.83

S&R -0.52 0.08

AIM -0.05 0.40

SSQ -0.02 0.41

SENSITIVITY TEMPORAL CONTEXT NO

CONTEXT

COGNITION 0.13 0.30 0.16 0.37

SENSITIVITY 0.29 0.22 0.42

TEMPORAL 0.20 0.38

CONTEXT 0.33

Correlations between level 2 factors

N200, effect of signal processing


SNR score, Hagerman sentences

Summary


• For auditory testing, it is important to provide audibility of the signal

• Testing with wearable hearing aids resembles real life but lack

control of several parameters and have generally a limited set of

options

• A centrally placed hearing aid ensures a controlled gain but have

several drawbacks

• A computer-Matlab based gain control facilitates controlled, cheap

and easy setup. Cannot be used with live signals and is

problematic with several sound sources

• The Master Hearing Aid system have the advantages of the Matlab

based system with the addition of using live signals and multiple

sources. Slightly more complex programming/setup and expensive.

Applied Auditory Research, Linköping University


www.liu.se

Stefan Stenfelt

a master hearing aid system for auditory tests of hearing impaired...

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