Speech recognition with varying numbers and types of competing talkers by normal-hearing, cochlear-implant, and implant simulation subjects

Cochlear-implant users perform far below normal-hearing subjects in background noise. Speech recognition with varying numbers of competing female, male, and child talkers was evaluated in normal-hearing subjects, cochlear-implant users, and normal-hearing subjects utilizing an eight-channel sine-carrier cochlear-implant simulation. Target sentences were spoken by a male. Normal-hearing subjects obtained considerably better speech reception thresholds than cochlear-implant subjects; the largest discrepancy was 24 dB with a female masker. Evaluation of one implant subject with normal hearing in the contralateral ear suggested that this difference is not caused by age-related disparities between the subject groups. Normal-hearing subjects showed a significant advantage with fewer competing talkers, obtaining release from masking with up to three talker maskers. Cochlear-implant and simulation subjects showed little such effect, although there was a substantial difference between the implant and simulation results with talker maskers. All three groups benefited from a voice pitch difference between target and masker, with the female talker providing significantly less masking than the male. Child talkers produced more masking than expected, given their fundamental frequency, syllabic rate, and temporal modulation characteristics. Neither a simulation nor testing in steady-state noise predicts the difficulties cochlear-implant users experience in real-life noisy situations.