Sam Gilman Assoc., P. O. Box 25176, W. Los Angeles, CA 90025
J. Phil Mobley
House Ear Inst., Los Angeles, CA 90057
An implantable hearing prosthesis is being investigated based on the conduction of sound through a liquid-filled tube directly from an electronics module into the cochlea, thus by-passing the external and middle ears completely. Hearing could be provided up to the functioning limits of the cochlea regardless of pathological or functional conditions of the external or middle ear. The system also has wide frequency response with low distortion at high sound levels. Scale model acoustic tests (described in an accompanying paper) confirmed the calculated performance. The band output is linear with applied transducer voltage up to more than 140 dB SPL, is flat ((plus or minus)5 dB) from 150 to 6000 Hz, rising 10 dB to 10 kHz and shows no standing waves. Transmission losses are essentially zero over the entire frequency range so that a maximum efficiency is obtainable. Biocompatible transmission liquid and tubing sizes and material are selected to match the specific acoustic impedance of the cochlea at the interface and couple most efficiently to the transducer.