Around 14% of the European population suffer from a noticeable degree of hearing loss and would benefit from some form of hearing assistance or deaf aid. Recent DDA legislation and requirements mean that many more hearing assistive systems are being installed – yet there is evidence to suggest that many of these systems fail to perform adequately and provide the benefit expected. This paper reports on the results of some trial acoustic performance testing of such systems. In particular the effects of system microphone type, distance and location are shown to have a significant effect on the resultant performance. The potential of using the Sound Transmission Index (STI) and in particular STIPa, for carrying out installation surveys has been investigated and a number of practical problems are highlighted. The requirements for a suitable acoustic test source to mimic a human talker are discussed as is the need to the need to adequately assess the effects of both reverberation and noise. The findings discussed in the paper are also relevant to the installation and testing of classroom ‘sound field’ systems and also boardroom type reinforcement systems and conferencing / teleconferencing systems.
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