Mandarin lexical tone recognition in bimodal cochlear implant users

Objective:To assess the recognition of lexical tones in Mandarin-speaking bimodal cochlear implant (CI) subjects. Design:Lexical tone recognition in quiet and noise (SNR= +5 dB) was measured with electric stimulation (CI alone) or bimodal stimulation (CI + hearing aid (HA)). The recognition and confusion rates of the four tones (T1, T2, T3 and T4) were analysed. Spearman correlation analysis was performed to examine the relationship between hearing levels in the contralateral ear and bimodal benefits. Study sample:Twenty native Mandarin-speaking bimodal CI users, with ages ranging from 16-49 years. Results:Relative to the CI alone, mean tone recognition with the CI + HA improved significantly from 84.1-92.1% correct in quiet (+8 points) and from 57.9-73.1% correct in noise (+15.2 points). Tone confusions between T2 and T3 were the most prominent in all test conditions, and T4 tended to be labelled as T3 in noise. There was no significant correlation between the bimodal benefits for tone recognition and the unaided or HA-aided pure-tone thresholds at 0.25 kHz. Conclusion:Listeners with CI + HA exhibited significantly better tone recognition than with CI alone. The bimodal advantage for tone recognition was greater in noise than in quiet, perhaps due to a ceiling effect in quiet.