Download Behind the Ear Placement - CAE Users

Tactile Auditory Sensory
Substitution
Jimmy Fong, Jack Page, Becky
Jones, Ryan Thome, Matt Valaskey
BME 301
March 9, 2007
Client:
Veronica H. Heide, Au.D.
Audible Difference
Advisor:
Mitchell E. Tyler, P.E., M.S.
Dept. of Biomedical Engineering &
Dept. of Ortho-Rehab Medicine
University of Wisconsin - Madison
High Frequency Hearing Loss





Sensorineural
Normal hearing =
50 – 20,000 Hz
Above 1,000 Hz is
lost
Loss of ability to
hear certain high
frequency
consonants
Like hitting piano
key with no
strings
Krames Communications.
Problem Statement
The goal is to design and develop an
auditory substitution device that through
the use of vibro-tactile stimulation can
substitute for regional frequency hearing
loss. The main focus of this semester is
integrating vibro-transducers into the
system in order to prepare the system for
laboratory trials.
Sensory Substitution

Presenting environmental information absent in
one sensory modality to another

Examples:



Long Cane - visual navigation substituted though touch
Sign Language - speech substitution through vision
Braille - visual text substitution though touch
Existing Devices

Tactaid 7



Tickle Talker


Electric shock on sides
of fingers
One electrode per range
of frequency
Vibro-tactile stimulation
on sternum, abdomen,
forearm or neck
Tacticon 1600
http://us.st11.yimg.com/us.st.yimg.com/I/audiologic
alengineering_1903_431188
PDS Summary
The device will substitute for high
frequency hearing loss to the extent of
helping the user in everyday
communication.
 Use vibro-tactile stimulation
 Self contained, portable, discrete or
aesthetically acceptable

System Diagram
Person
Speaking
Audio Waves
Microphone
Analog
Voltage
Signal
Multi-channel
Amplifier/
Comparator
Digital Signal
Analog Voltage
Signal
Sound Card
Amplified
Analog
Voltage
Signal
Transducers Vibrational Pulses
User
Cool Edit
Digital Signal
that has been
filtered to
specified
frequency,
amplitude,
and channel
divisions
Word Discrimination

Pairs of words that
can be distinguished
with device




Sixty versus Fifty
Shirt versus Church
Much versus Such
Sob versus Shop


Audio input is filtered
for specific frequency
range
Becomes separate
channels




1:
2:
3:
4:
1.6-2.0
2.0-3.0
3.0-3.5
4.5-8.0
kHz
kHz
kHz
kHz
–
–
–
–
p, i, m
ch, sh
f
s, th
Sound Processing
Unfiltered Sound Wave
“Sixty – Fifty”
Frequency Filtered Sound Waves
Vibro-tactile Stimulation
Substitute hearing loss with vibration
 Need to stimulate subcutaneous
mechanoreceptors: Pacinian Corpuscles
(FA II)

Vibro-tactile Stimulation




Konyo study indicates minimum threshold for detection:
 1 mm displacement @ ~5 Hz
 1 μm displacement @ ~200 Hz
Increased sensitivity at vibrations of 60 and 250 Hz
Density of mechanoreceptors less behind ear
Two point discrimination test
Vibro-tactile Stimulation



Series of 4 piezoelectric transducers
Transducer deflects varying with frequency input
Allows user to discern different phonemes by location of
the stimulus
Vibro-tactile Pros & Cons

Pros





Comfortable compared to electro stimulation
Less variation in sensation
Cost effective
Ease of implementation
Cons


More power consumption
Larger 13 mm x 25 mm per electrode
Electro-tactile Stimulation

Create vibrating sensation by sending
small currents through the skin

Typical currents range from 1-20 mA

Comfortable frequency around 15 Hz

High voltage (200 – 500 V) necessary to
create current

Typical electrodes are gold or silver plated and
a few millimeters in diameter
Electro-tactile Pros & Cons

Pros



Small power consumption
As small as 3 mm in diameter
Cons



Less comfortable than vibro stimulation
More variation in sensation
Complex implementation
Behind the Ear Placement

Specifications

Skull to skull and skin to skin tactors 25 mm
apart unless stimulating at different
frequencies

Skull to skin tactors 20 mm apart

2 tactors on skull bone, 2 on skin below

Learning curve to sensing the stimulations
Determining Consonants

Which stimulator should be activated?

Frequency approach


Stimulators and consonants related to certain
frequencies
Linguistic approach



Consonants are variable and affected by neighboring
sounds
Utilize voice recognition to determine specific
consonants
Relate stimulation pattern to a linguistic sound or
symbol
Design Matrices
Stimulation
Vibro
Electro
Power Consumption (10)
5
9
Safety (5)
4
4
Ease of Implementation (10)
9
2
Patient Comfort (5)
4
2
Aesthetics (5)
2
4
24
21
Frequency
Linguistic
Accuracy (10)
7
8
Ease of Implementation (10)
9
1
Noise Adaptability (5)
2
4
Processing Time (5)
4
2
Cost (5)
5
2
27
17
Total
Speech Analysis
Total
Future Work
Integrate tactile transducers with circuit
 Perform further speech analysis to better
isolate fricative sounds
 Test efficacy of device on human subjects
 Miniaturize
 Further test effectiveness of device
placements on body

References



Krames Communications. (1995). Hearing Aids.
[Brochure]. San Bruno, CA.
Audiological Engineering Corp. (n.d.) Tactaid 7.
Retrieved 29 September, 2006 from
http://www.tactaid.com/tactaid71.html.
Kanyo, M. et al. 2005. A Tactile Synthesis Method
Using Multiple Frequency Vibrations for
Representing Virtual Touch. IEEE/RSJ. p 1121 –
1127.