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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
April 2007 Copyright 2007 Pivit Technologies Inc. 4
Team Members
David Dickin – CEO
Mehran Eghtesad – Senior Hardware Designer
Ryan Dickie – Senior Software Designer
Merle Kinkade – CFO
April 2007 Copyright 2007 Pivit Technologies Inc. 5
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
April 2007 Copyright 2007 Pivit Technologies Inc. 7
Subsystems
I/O Control Board
Parallel Port Interface
VibraPadAudio
Processing and GUI
Tactile Hearing Aid (THA)
April 2007 Copyright 2007 Pivit Technologies Inc. 9
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
April 2007 Copyright 2007 Pivit Technologies Inc. 11
Audio IO
Runs in separate threads 44100 Hz, 16-bit, mono Can load/save to wav files
Can use microphone input
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DSP
Hamming Windows R2C DFT with N = 4096 Threshold Filtering Critical Transform Bins
Buzzer Amplitude Mapping
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Parallel Port Interface
Runs in a separate thread Updates in 1ms intervals Buzzer amplitude achieved by pulsing buzzers
Uses inpout32.dll driver
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I/O Control Board
PCB fabricated to drive vibrators
Connects software to VibraPad UI is on/off switch and intensity knob
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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
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Proposed Mappings
Uniform
Offset
Offset with Snaking
Offset with Snaking & Natural Mapping
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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
April 2007 Copyright 2007 Pivit Technologies Inc. 19
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
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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.
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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
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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
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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
April 2007 Copyright 2007 Pivit Technologies Inc. 28
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?
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Experiment 2 Procedure
Changes from Experiment 1 30 short sound clips Normalize length of clips (3-4 sec)
Subject not allowed to hear sounds
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Experiment 2 Results
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?
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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)
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Vibrator Layout
Experiment 1/2 Layout
Experiment 3 Layout
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Experiment 3 Procedure
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
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Experiment 3 Results
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
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Experiment 3 Results
Previous exposure• Our group: 97.5%• Everyone else: 61%
Age• 16 Individuals under 35: 77%
• 7 individuals over 35: 44%
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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
April 2007 Copyright 2007 Pivit Technologies Inc. 38
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
April 2007 Copyright 2007 Pivit Technologies Inc. 41
Bark Scale Divisions
http://ccrma.stanford.edu/~jos/bbt/Bark_Frequency_Scale.html