Tactile Auditory Sensory Substitution Ryan Thome, Sarah Offutt, Laura Bagley, Amy Weaver, Jack Page BME 200/300 December 8, 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

Abstract High frequency hearing loss is a problem common among people of all age groups. People suffering from this type of hearing loss often lose the ability to hear certain consonant sounds, and as a result have difficulty communicating with others. The goal of the project is to use sensory substitution, a technique for presenting environmental information missing in one sensory modality to another, to help replace this missing high frequency information. The device takes recorded information, filters it into four different channels based on frequency, then outputs all four channels to a sound card. The sound card outputs to a circuit that amplifies the sound and reduces the noise. The circuit then outputs to four transducers. Use of this device, in conjunction with the lower frequency audio information gathered directly by the user, should allow the user to better communicate by speech and hearing.

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, in order to aid in daily communication needs.

Sensory Substitution  Presenting environmental information absent in one sensory modality to another  Examples: Long Cane - visual navigation substitution through touch Sign Language - speech substitution through vision Braille - visual text substitution through touch

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 alengineering_1903_431188

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.

System Diagram Amplified Analog Voltage Signal Analog Voltage Signal Digital Signal that has been filtered to specified frequency, amplitude, and channel divisions Analog Voltage Signal Microphone Cool Edit Person Speaking Sound Card Multi-channel Amplifier Transducers User Audio Waves Vibrational Pulses Digital Signal

“Cool Edit” Software  Audio input is filtered for specific frequency range  Becomes separate channels 1: kHz – p, i, m 2: kHz – ch, sh 3: kHz – f 4: kHz – s, th

Sound Card  Turtle Beach Audio Advantage Roadie  Able to output up to six channels  Voltage output mV

Circuit  Parts Four comparators Four transducers 10kΩ and 1kΩ Resistors  Amplifies signal  Reduces noise  Initial voltage output 0-50mV  Amplified 11x  Current draw 0-2mA

Output  Piezoelectric buzzers  Placed on neck with Bioflex ® adhesive  Transducers buzz if amplitude in that channel exceeds a voltage of 1 V

Word Discrimination  Joe took father’s shoe bench out he was sitting on my lawn.  Pairs of words that can be distinguished with device Sixty versus Fifty Shirt versus Church Much versus Such Sob versus Shop

Word Pairs Sixty - Fifty Much - Such

Future Work  Acquire and implement vibro-stimulators  Minimize size  Real time  Specific sound analysis

References  Audiological Engineering Corp. (n.d.) Tactaid 7. Retrieved 29 September, 2006 from  Better Hearing Institute (BHI). Hearing Loss- The Prevalence of Hearing Loss Date Vistied: 10/13/  Fairbanks, G. Voice and Articulation Drill Book. Harper & Row Publishers; New York, Pages  Kaczmarek, K. A., Webster, J. G., Bach-y-Rita, P. and Tompkins, W. J. Electrotactile and vibrotactile displays for sensory substitution systems  Krames Communications. (1995). Hearing Aids. [Brochure]. San Bruno, CA.  “Piezoelectric Transducers.” NDT Resource Center. 19 October s.htm.  Scapa. (2006). Bioflex. Retrieved 31 November, 2006, from  Webster, John G. (2003). Bioinstrumentation. Indianapolis, IN: John Wiley & Sons Inc.