Implementation of a Microprocessor-Based Tactile Hearing Prosthesis

A microprocessor-based tactile vocoder is described that offers important advantages over its analog counterpart. Digital implementation provides more flexibility and precision. The system simulates, in real-time, the characteristics of a 16-channel tactile vocoder developed at Queen's University in Kingston, Ont., Canada and is intended for use with a linear array of 16 miniature vibrators. Design considerations of the circuit logic, program structure, and algorithms used to implement the vocoder and the performance characteristics such as the dynamic range and noise of the various algorithms are discussed. The overall system has a noise level less than -60 dB re the maximum input and the bandwidth is 7.5 kHz. The system will first be used in the laboratory and in the classroom with two microphones and two tactile displays. Future plans call for the design to be adapted to lower power devices, when they become available, to achieve a single-display, wearable version that can be evaluated under natural conditions of acoustic signal and noise.