Psychophysical Performance and Mandarin Tone Recognition in Noise by Cochlear Implant Users

Objective: The present study was aimed to examine the relationship between psychophysical perfor-mance in temporal and spectral resolution and Mandarin tone recognition in noise by cochlear-implant (CI) listeners. Design: Seventeen Nucleus-24 implant users, 10 postlingually deafened and 7 prelingually deafened, participated in the experiments. A 3-interval, forced-choice procedure was used to measure gap detec-tion and pure-tone frequency discrimination at 250 to 4,000 Hz in octave steps. A 4-alternative forced-choice procedure was used to measure Mandarin tone recognition in quiet and in noise. Signal-to-noise ratios (SNRs) varied from 10 to –10 dB. All stimuli were delivered to the clinical processor via a speaker in a sound free field. The obtained data were compared to data collected from normal-hear-ing control subjects, as well as cochlear-implant users who performed similar tasks using single-electrode stimulation via a research interface. Results: Postlingually-deafened CI subjects gener-ally performed better than prelingually-deafened subjects. The average gap detection threshold was 30 ms with a range from 4 to 128 ms. The average frequency difference limen was 100 Hz with a range from 12 to 192 Hz, regardless of the standard fre-quency. The average tone recognition was 80 % cor-rect in quiet, which dropped to 55 % at 10 dB SNR and essentially chance performance at –5 dB SNR. In comparison, the normal-hearing control subjects maintained essentially perfect performance over this SNR range. Only frequency discrimination at 1,000 Hz was significantly correlated with tone rec-ognition in quiet but all psychophysical measures were correlated to tone recognition in noise. Conclusions: The present result suggests that the CI users can rely on either temporal or spectral cues to perform tone recognition in quiet, but need both cues for tone recognition in noise. Future CI proces-sors need to extract and encode these acoustic cues to achieve better performance in tone perception and production. (Ear & Hearing 2007;28;62S–65S) The last decade has observed rapid development in cochlear implants in China, from essentially a nonexistence of multichannel cochlear-implant (CI) users to more than 1,000 users today (Cao, 2004