The influence of non-linear frequency compression on music perception for adults with a moderate to severe hearing loss

Abstract

Objective: To date, the main focus in frequency lowering hearing aid studies has been in relation to speech perception abilities. With improvements in hearing aid technology, there is a growing interest in musical perception as a dimension that could improve hearing aid users’ quality of life. The purpose of this study was two-fold: Firstly, to develop a test of music perception for adult hearing aid users and secondly, to evaluate the influence of non-linear frequency compression (NFC) on music perception with the use of the Music Perception Test (MPT) compiled by the researcher. Research design and research sample: Phase 1 entailed the compilation of the MPT and can be described as design-based. A quasi-experimental research design was selected to establish the structure of the method employed in Phase 2, which involved the fitting of participants (n=40) with NFC hearing aids. Objective data was obtained with the hearing aids with NFC active and inactive. Phase 3 was characterized by a survey design which elicited subjective impressions of the participants’ musical experiences with NFC active and inactive. Results: Results proved that normal hearing adults as well as adults using hearing aids were able to complete all the sub-tests of the MPT. Furthermore, the use of NFC resulted in a statistically significant improvement in hearing aid users’ perception of timbre and melody, but not of pitch. Overall, no statistically significant improvement in their perception of rhythm was observed, although their performance on some rhythm sub-tests improved significantly. The use of NFC also brought about a statistically significant improvement in hearing aid users’ perception of the music qualities of overall fidelity, tinniness and reverberance. Although participants experienced the loudness, fullness, crispness, naturalness and pleasantness of music more positively with NFC, these benefits were not statistically significant. Conclusion: The MPT can be used successfully for assessing music perception in hearing aid users within the South African context and may therefore result in more accountable hearing aid fittings. The use of NFC may increase hearing aid users’ appreciation of music whilst not influencing music perception negatively. Given that a large percentage of hearing aid users express a loss in enjoyment of music, audiologists should not ignore the possible benefits of NFC, especially if one takes into account that previous research indicated speech perception benefits with this technology.