Some effects of room acoustics and background noise on assistive listening systems and devices

Abstract

Approximately 10–14% of the general population (United States and Northern Europe) suffer from a noticeable degree of hearing loss and would benefit from some form of hearing assistance or deaf aid. However, many hearing aids do not provide a suitable level of intelligibility when used in large reverberant or noisy spaces and rooms. The paper investigates the acoustic and speech intelligibility requirements for Assistive Listening Systems that may be used separately or in conjunction with a hearing aid to improve the potential intelligibility of the received speech signal. A number of microphone pick-up scenarios have been investigated and are reported in terms of their potential intelligibility and sound quality performance. The results of testing carried out in a number of rooms and venues are presented, mainly in terms of the resultant Speech Transmission Index (STI). The paper concludes by providing a number of recommendations and guidelines for successful microphone placement and introduces a novel technique for establishing useful talker sound radiation and hence microphone target aiming.