THE RELATIONSHIP BETWEEN LISTENING CONDITIONS AND ALTERNATIVE AMPLIFICATION SCHEMES FOR MULTIPLE MEMORY HEARING-AIDS

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 consiste d of three laboratory tests: 1) A screening test to select hearing imp aired subjects who appeared to benefit from multiple amplification sch emes. 2) A category scaling test to rank 16 amplification schemes in 1 5 listening conditions. The 16 schemes were simulated with a digital m aster hearing aid and comprised 5 Linear systems and 11 compression ch aracteristics. The 15 listening conditions comprised 6 listening envir onments combined with 2 or 3 response criteria. 3) A paired comparison test in which the two highest ranked amplification schemes were evalu ated together with a reference linear frequency response (NAL) in a ro und-robin test. Results: The screening test demonstrated that 21 heari ng impaired people out of 25 with mild or moderate, flat or gently slo ping hearing losses appeared to benefit from multiple amplification sc hemes. Age or audiometric factors did not serve to discriminate betwee n those who selected different schemes and those who did not. In gener al, the NAL-response was preferred or was as good as any other for lis tening to speech in quiet, speech in reverberation, speech in babble-n oise, and for naturalness of all listening environments. The subjects consistently selected an amplification scheme other than the NAL-respo nse for four specific listening conditions. The findings suggest that substantial high-frequency compression is preferred for the ease of un derstanding multiple talkers, whose voices differ in overall level, in quiet environments. The annoyance of low-frequency background noise c an be reduced by low-frequency compression, whereas a frequency respon se steeper than the NAL-response makes it easier to understand speech in low frequency background noise. Finally, a frequency response flatt er than the NAL-response can be used to make a high-frequency backgrou nd 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 amplificat ion schemes depending on the number of talkers, the background noise a nd the response criterion.