Effects of harmonicity on Mandarin speech perception in cochlear implant users

Previous research has demonstrated the negligible impact of harmonicity on English speech perception for normal hearing (NH) listeners inquiet environments. This study aims to bridge the gap in understanding the role of harmonicity in Mandarin speech perception for cochlear implant (CI) users. Speech perception inquiet was tested in both CI simulation group and actual CI user group using harmonic and inharmonic Mandarin speech. Furthermore, speech-on-speech perception was tested in NH, CI simulation, and actual CI user groups. For speech perception in quiet, results show that, compared to harmonic speech, inharmonic speech decreased the mean recognition rate for both actual CI user and CI simulation groups by about 10 percentage points. For speech-on-speech perception, all groups (i.e., NH, CI simulation, and actual CI user) performed worse with inharmonic stimuli compared to harmonic stimuli. The findings of this study, along with previous studies in NH listeners, indicate that harmonicity aids target speech recognition for NH listeners in speech-on-speech conditions but not speech perception inquiet. In contrast, harmonicity plays an important role in CI users' Mandarin speech recognition in both quiet and speech-on-speech conditions. However, under speech-on-speech conditions, CI users could only understand target speech at positive SNRs (often > 5 dB), suggesting that their performance depends on the intelligibility of the target speech. The contribution of harmonicity to masking release in CI users remains unclear.