A prototype hearing aid for acoustic coupling of telephone and hearing aids

Abstract

Recent trends in the telecommunications industry have resulted in an increased number of telephone receivers which are not compatible with the induction coils contained in many hearing aids. This situation has developed in spite of efforts by the Federal Government to legislate telephone/hearing aid compatibility. This project was designed to evaluate a prototype heating aid with specialized frequency shaping capability. In short, we wished to discover if current technologies were capable of creating a hearing aid which could be effectively used by hearing aid wearers to understand speech transmitted over a telephone without the use of magnetic coupling. Ten subjects from three different hearing loss categories: precipitous high‐frequency loss, sloping high‐frequency loss, and relatively flat, severe loss, were tested. Subjects were evaluated using three types of frequency shaping: “typical hearing aid response,” low‐frequency compensation, and flat gain condition (up to 40 dB of linear amplification beyond that normally required for free‐field communication). Subjects were required to respond to recordings of the NU‐6 WORD LIST presented in quiet and with 45 dB and 55 dB SPL of competing background noise (multitalking noise). The results of this study suggest that certain classes of hearing impairment may benefit from specialized circuitry which provides frequency shaping to the telephone signals received at the hearing aid microphone. This technique has also been shown to even be effective in moderate amounts of background noise, allowing speculation that acoustic coupling of hearing aids and telephones may be more realistic than commonly thought.