Electroacoustic Performance Requirements for Assistive Listening Systems for Hard of Hearing and Hearing Impaired Listeners

Around 10 - 14% of the general population (USA & Northern Europe) suffer from a noticeable degree of hearing loss and would benefit from some form of hearing assistance or deaf aid. Disability legislation and requirements in many countries mean that many more hearing assistive systems are being installed - yet there is continuing evidence to suggest that many of these systems fail to perform adequately and provide the benefit expected. In particular Assistive Listening Systems (ALS) provided in many theaters, concert halls and similar auditoria are often not primarily designed with the hearing impaired in mind but rather are an adjunct to a show relay, back of house communications system. Even where Assistive Listening is the primary function many systems still fail to deliver an appropriate signal or adequate intelligibility. The paper reviews current practice and puts forward a number of guideline proposals that will hopefully help improve the situation. In particular, speech intelligibility requirements are addressed.