The Relationship Between Listening Conditions and Alternative Amplification Schemes for Multiple Memory Hearing Aids

In Brief Objective The aim of this study was to determine a relationship among selected listening conditions and amplification schemes that could be provided in a multiple memory hearing aid. Design The study consisted of three laboratory tests: 1) A screening test to select hearing impaired subjects who appeared to benefit from multiple amplification schemes. 2) A category scaling test to rank 16 amplification schemes in 15 listening conditions. The 16 schemes were simulated with a digital master hearing aid and comprised 5 linear systems and 11 compression characteristics. The 15 listening conditions comprised 6 listening environments combined with 2 or 3 response criteria. 3) A paired comparison test in which the two highest ranked amplification schemes were evaluated together with a reference linear frequency response (NAL) in a round-robin test. Results The screening test demonstrated that 21 hearing impaired people out of 25 with mild or moderate, flat or gently sloping hearing losses appeared to benefit from multiple amplification schemes. Age or audiometric factors did not serve to discriminate between those who selected different schemes and those who did not. In general, the NAL-response was preferred or was as good as any other for listening to speech in quiet, speech in reverberation, speech in babble-noise, and for naturalness of all listening environments. The subjects consistently selected an amplification scheme other than the NAL-response for four specific listening conditions. The findings suggest that substantial high-frequency compression is preferred for the ease of understanding multiple talkers, whose voices differ in overall level, in quiet environments. The annoyance of low-frequency background noise can be reduced by low-frequency compression, whereas a frequency response steeper than the NAL-response makes it easier to understand speech in low frequency background noise. Finally, a frequency response flatter than the NAL-response can be used to make a high-frequency background noise sound less annoying. Conclusion Hearing aid users with mild or moderate, flat or gently sloping hearing losses, fitted with equal and sufficient variation in amplification, prefer different amplification schemes depending on the number of talkers, the background noise and the response criterion. Determining the benefit from amplification in different listening situations remains a complex problem. We assessed whether listeners with mild or moderate hearing losses prefer different amplification schemes in different listening environments, observing that the preferred scheme did vary as a function of factors such as the numbers of talkers, the background noise, and response criterion. Results support the value of multiple-memory hearing aids that allow individuals to alter the characteristics of the amplification in different listening environments. Gitte Keidser