1. Tactile Auditory Sensory Substitution Jimmy Fong, Jack Page, Becky Jones, Ryan Thome, and Matt Valaskey Client: Veronica H. Heide, Au.D. Advisor: Mitchell E. Tyler 2 Problem Statement Design and develop an auditory substitution device that through the use of vibrotactile stimulation can substitute for regional frequency hearing loss. 3 Background 1 Abstract High frequency hearing loss is a problem common among people of all age groups. People who suffer from this type of hearing loss often lose the ability to hear certain consonant sounds. The goal of this project is to replace the missing high frequency information using sensory substitution, a technique for presenting environmental information missing in one sensory modality to another. 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. 8 Future Work -Develop system for training with device-Test efficacy of device on human subjects -Implement real-time sound processing-Further testing of tactile placement area -Miniaturize device -Normal hearing = 50 – 20,000 Hz -High-frequency hearing loss = Above 1,000 Hz is lost -Categorized as sensorineural hearing loss -Loss of ability to hear certain high frequency consonants 4 Design Specifications -Help the user in everyday communication situations -Use tactile stimulation -Self contained -Portable -Discrete and aesthetically acceptable 5 Proposed Design Design Overview Device layout 1: 1.6-2.0 kHz – p, i, m 2: 2.0-3.0 kHz – ch, sh 3: 3.0-3.5 kHz – ch, f 4: 4.5-8.0 kHz – s, th Channel to Frequency Breakdown -Observe vibration pattern of specific words and consonant sounds -Pairs of words that can be distinguished with device Sixty versus FiftyKit and Tick Shirt versus ChurchSit and Tip Kite and TiedSob versus Shop 6 Prototype 7 Testing Vibrating Motor -12mm diameter, 3.4mm thick -1G vibration -12,000 RPM -Requires < 3V and < 50mA Device Placement-Behind Ear -Point discrimination test on that area-Tactors 1 and 2 are on the mastoid process 30 mm apart -Tactors 2 and 3 are 25 mm apart -Tactors 3 and 4 are on the skin below the mastoid process and are 30 mm apart -The distances are based on a two-point discrimination test 4 3 2 1 25mm 30mm Attachment Considerations 1) Long or short term Adhesive -Made for direct skin application -Comfortable, easy to apply 2) A hook or headband apparatus Sound Processing Circuit Design Vibrotactile Motors Microphone Sound Card Software Filtering Sound Card Amplifier Comparator Adding Inverter Monostable Motor LED Circuit schematic for each audio channel: - 1 st Stage: Amplifies signal with a gain of ~ 50 -2 nd Stage: Comparator that saturates at +9 V when signal > 1 V - 3 rd Stage: Inverting summer that adds a -9 V offset and inverts signal -4 th Stage: High input impedance buffer -5 th Stage: 555 timer in monostable configuration to provide a square wave voltage to the motor -Remove without skin trauma -Resistant to dirt and moisture -Excellent adhesion to skin “Sixty – Fifty” -Runs on two 9 V batteries -Current draw: ~ 150 mA -Expected battery life: ~ 12 hr Costs: Circuit Components: $10.16 Roadie Sound Card: $49.99 Motors: $15.96 Attachment: $2.00 Total: 78.11 Acknowledgements We would like to thank Dr. Veronica Heide and Prof. Mitch Tyler for their patient guidance as well as Prof. L. Burke O’Neal and Amit Nimunkar for their circuit expertise.