Influence of amplification scheme and number of channels on aided speech-intelligibility performance

Abstract

Modern hearing aids offer a wide range of channels (i.e., filters) and amplification schemes. Our previous work revealed that increasing the number of channels, in conjunction with a fast-fast amplification scheme, results in (a) the spectral flattening of the vowels /i, u, ^/ (Amlani et al., 2011), and (b) reduced consonant- and vowel-identification accuracy in impaired listeners (Amlani et al., 2012). In the present study, we assess the performance of impaired listeners and their normal-hearing controls on the perception of everyday speech using the Connected Speech Test (Cox et al., 1987, 1988). The stimuli were processed through a simulated hearing aid with varying amplification schemes (linear, compression [fast-fast, slow-slow, fast-slow]) and number of channels (2, 8, 16). Findings revealed that while speech-intelligibility performance improved markedly with everyday speech compared to /CVC/ words for both groups, normal-hearing listeners identified the target words significantly better than impaired listeners did. Speech-intelligibility performance was similar across number of channels for normal-hearing listeners, but decreased significantly with a fast-fast amplification scheme. For impaired listeners, performance declined for channels greater than 2 and with the inclusion of the fast-fast amplification scheme. We discuss the implication of these findings relative to clinical application and hearing aid design.