Perceptual Loudness Growth in Cochlear Implant Users

Abstract

Purpose: Despite a growing number of cochlear implant (CI) studies, little attention has been given to loudness perception. The overall purpose of this study is to obtain the perceptual loudness growth from CI users and systematically investigate it with other relevant variables.Methods: Fourteen CI users and 14 normal hearing (NH) adults participated in this study. Loudness growth functions were obtained using three warble tones presented at 500 Hz, 1 kHz, and 4 kHz. Sentence recognition tests were implemented under favorable and adverse noise conditions. Mapping parameters including T-level, C-level, and electrical dynamic range were analyzed in conjunction with outcomes from the loudness growth.Results: The loudness growth curves for CI group were sharper than those for NH group. CI group showed a narrower acoustic dynamic range than NH group. There was no significant relationship between acoustic dynamic range and electrical dynamic range for CI users. Sentence recognition scores in adverse noise conditions were associated with electrical dynamic range in CI users. In NH group, a significant positive relationship was found between sentence recognition scores in adverse condition and acoustic dynamic range.Conclusion: This study showed that the perceptual loudness growth of CI users is not identical to that of NH adults, due to the unique way of signal processing mechanisms. Acoustic dynamic range for CI users seems affected by gain control algorithms. The adjusting mapping parameters associated with loudness may improve speech perception performance regardless of the dynamic range of CIs.