Performance of Individual Hearing Aids Utilizing Microphone and Induction Coil Input

Abstract

Physical measurements of gain, maximum power output, frequency response, and harmonic distortion were made on each of two body-type hearing aids on both the microphone and induction coil settings. In addition, we investigated speech intelligibility through each aid, for both acoustic and magnetic input, using 32 normal-hearing subjects. Our findings indicated that different hearing aids provide different sensitivity for loop induction. For a given hearing aid, physical characteristics varied between the microphone and the telephone coil settings. The intelligibility of speech produced by a given mode of signal input, either microphone or telephone coil, was dependent on physical characteristics of the hearing aid. The usable high-frequency response and the configuration of the response curve in the region of 1500 to 3000 Hz appeared to be associated with the intelligibility of monosyllabic words.