tactile hearing aid demonstration ensc 440 – group 14 david dickin mehran eghtesad ryan dickie...

Tactile Hearing Aid Demonstration

ENSC 440 – Group 14

David DickinMehran EghtesadRyan DickieMerle Kinkade

Simon Fraser UniversityApril 2007

April 2007 Copyright 2007 Pivit Technologies Inc. 2

Outline

Introduction Software Subsystems Hardware Subsystems Business Case Experimental Results Conclusion Demonstration

Introduction


Team Members

David Dickin – CEO

Mehran Eghtesad – Senior Hardware Designer

Ryan Dickie – Senior Software Designer

Merle Kinkade – CFO


What is a Tactile Hearing Aid?

A device that translates noise into touch

Used to help the hearing impaired

Traditional hearing aids cannot be used by all people


System Overview


Subsystems

I/O Control Board

Parallel Port Interface

VibraPadAudio

Processing and GUI

Tactile Hearing Aid (THA)

Software Subsystems


Technologies

Wav Reader/Writer: self-designed. FFT: FFTW (Fastest Fourier Transform in the West)

Audio Input/Outer: Windows Multimedia Library

Parallel Port: Inpout32.dll Drawing: GDI GUI : Winapi Misc: Boost C++ libraries


GUI User Interface


Audio IO

Runs in separate threads 44100 Hz, 16-bit, mono Can load/save to wav files

Can use microphone input


DSP

Hamming Windows R2C DFT with N = 4096 Threshold Filtering Critical Transform Bins

Buzzer Amplitude Mapping


Parallel Port Interface

Runs in a separate thread Updates in 1ms intervals Buzzer amplitude achieved by pulsing buzzers

Uses inpout32.dll driver

Hardware Subsystems


I/O Control Board

PCB fabricated to drive vibrators

Connects software to VibraPad UI is on/off switch and intensity knob


VibraPad

Why 16 Vibrators?• Parallel port limitations• Space limitations• Power restrictions

Worn on stomach/torso area• Largest even surface area without contour issues

• Large network of nerve endings

Velcro for repositioning and ease of array placement


Proposed Mappings

Uniform

Offset

Offset with Snaking

Offset with Snaking & Natural Mapping


Transforms/Mapping

Critical Bands based on Frequency Response of Human Ear

Critical Band Mapping based on Bark Scale

Below 500Hz Uniform bands of 100Hz intervals

Above 500Hz Bands increase non-uniformly with Frequency


Bark Scale Divisions

High resolution below 500Hz

Human voice ~500Hz–2kHz

Optimum range ~2kHz–4kHz

Resolution decreases Rapidly above 4kHz http://ccrma.stanford.edu/~jos/bbt/

Bark_Frequency_Scale.html

Business Case


Budget and Funding


Schedule


Market Overview

Statistics obtained from publications of the National Institute on Deafness and other Communication Disorders (NIDCD) based on the American population and published at http://www.employmentincentives.com/state_incentives/documents/statistics_about_hearing_loss.doc.

Experimental Results


Goals

Goals“The purpose of this project is to determine

the extent and limitations of the tactile sensory system to receive and translate sound information. Such measures will be quantified by outlining specific test procedures and conducting these tests on several individuals.” Project Proposal

Criteria for Success“To deem a series of experiments successful, a

minimum hit rate of 80% must be achieved after a maximum of 100 minutes of cumulative training, or 5 iterations of the above experiment.” Design Specifications


Experiment 1 Procedure

10 short sound clips• Sirens, bells, animals, vehicles, etc.

Subjects allowed to hear sounds Training time

• One by one with audio: open ended• One by one without audio: open ended• Random: max 10 minutes• Operator-assisted training: max 10 minutes

Two set of Transforms


Transforms

Transform 1:• Frequency bins determined based on critical bands

Transform 2:• Frequency bins divided equally in log scale

Buzzer Frequency Range (Hz)

Transform 1 Transform 2

1 0-200 50-74

2 201-400 75-107

3 401-630 108-157

4 631-770 158-230

5 771-920 231-336

6 921-1080 337-491

7 1081-1270 492-719

8 1271-1480 720-1052

9 1481-1720 1053-1540

10 1721-2000 1541-2253

11 2001-2320 2254-3296

12 2321-2700 3297-4822

13 2701-3150 4823-7056

14 3151-3700 7057-10325

15 3701-4400 10326-15105

16 4401-15500 15106-22100


Experiment 1 Results

Conducted on 4 people Transform 1:

• Average Hit rate: 95%• Average Training time: 20 min• PASS

Transform 2:• Average Hit rate: 100%• Average Training time: 16 min• PASS

TOO EASY?



Changes from Experiment 1 30 short sound clips Normalize length of clips (3-4 sec)

Subject not allowed to hear sounds



Conducted on 4 people Transform 1:

• Average Hit rate: 55%• Average Training time: 43 min• FAIL

Transform 2:• Average Hit rate: 53%• Average Training time: 35 min• FAIL

TOO HARD?


Redesign Changes

Based on user feedback and comments as well as our personal observations

Create Transform 3: compromise of uniform and critical band

Change VibraPad layout Change different intensity levels (PWM)


Vibrator Layout

Experiment 1/2 Layout

Experiment 3 Layout



Large scale test (20+ subjects) 10 short sound clips of the same length• Sirens, bells, alarms, cars, etc.

Limited training time• Self directed: 7 minutes• Operator-assisted: 7 minutes

Provide a list of sound names to subjects

Using transform 3



Conducted on 23 individuals Average hit rate: 68% Average training time: 17.5 min

0 0

2

5

0

3

4

3

2

4

Hit rate (%)

# T

es

t S

ub

jec

ts



Previous exposure• Our group: 97.5%• Everyone else: 61%

Age• 16 Individuals under 35: 77%

• 7 individuals over 35: 44%

Conclusion


Summary

Participants are able to identify sounds with practice

High pitched sounds, like alarms, are easy to distinguish

More testing required, but has some marketability

Project stayed on schedule and budget


Acknowledgements

Thanks to the ESSEF and the Wighton Fund for funding for our project

Thanks to the ENSC 440/305 Professors and TA’s for their time and assistance


Questions?

Go Canucks!Go Canucks!


Similar Devices

Audiotact Tacticon Tactaid


Bark Scale Divisions

http://ccrma.stanford.edu/~jos/bbt/Bark_Frequency_Scale.html


Standards

Standards Council of Canada

CSA ANSI ISO FCC ECMA

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