Tactile Auditory Sensory
SubstitutionRyan Thome, Sarah Offutt, Laura Bagley, Amy Weaver, Jack Page
BME 200/300October 20, 2006
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
Problem StatementThe goal is to design and develop an auditory substitution device that through the use of a digital hearing aid and either vibro- or electro-tactile stimulation can substitute for regional frequency hearing loss.
PDS Summary Adjusts to user specific hearing loss Works with digital hearing aid output Use vibro- or electro- tactile stimulation Not highly noticeable (discrete or
aesthetically acceptable)
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
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.
Existing Devices Tickle Talker
Electric shock on sides of fingers
One electrode per range of frequency
Tactaid 7 Vibro-tactile stimulation
on sternum, abdomen, forearm or neck
Tacticon 1600
http://us.st11.yimg.com/us.st.yimg.com/I/audiologicalengineering_1903_431188
Digital Hearing Aid Two main types:
In-the-ear (ITE)Behind-the-ear (BTE)
Frequency range 100 Hz – 7300 Hz Takes analog waveform and converts it to
string of numbers Gain processing, digital feedback
reduction, noise reduction, speech enhancement
Sound Processing Unit Obtains high frequency signal from
hearing aid Amplifies signal Several channels of frequency Channel signals corresponding tactile
stimulus to fire
Electro- vs. Vibro-Tactile Stimulation Electro- Pros
Less power consumption – 1.2mW per 3 mm electrode
Smaller Easier construction
Cons Potential for shock and
burns (only @ v. large current)
Sensation quality varies Limited dynamic range
of sensation
Vibro- Pros
Less variation in sensation
Comfort
Cons More power
consumption - 138 mW per 4 mm electrode
Harder to attach More complex
construction
Placement In the ear
Pros Completely concealed from outsiders
Cons Less space for differentiation More complex construction
Behind the ear Pros
Mostly concealed from outsiders Easy access to hearing aid
Cons Attachment impeded by hair
Neck Pros
Most space for tactile layout Easiest construction
Cons Easily noticeable to outsiders
Proposed DesignElectro-BTE
• Array of electrodes aligned vertically behind ear
• Each electrode corresponds to certain frequency range
• As frequency increases each corresponding channel signals the electrode
Future Work Decide on components Design and build signal processing unit Determine two point discrimination
threshold Analyze signal from hearing aid and break
into channels
Design MatrixElectro-Neck
Vibro-Ear Electro-Ear
Power Consumption
5 1 5
Safety 4 5 4Ease of Manufacturing
4 2 4
Patient Comfort
3 4 4
Aesthetics 2 4 4
Total 18 16 21
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.