Importance of pitch and periodicity to Chinese-speaking cochlear implant patients

The study examines the relative importance of pitch and periodicity to Chinese speech recognition by normal-hearing subjects listening to a cochlear implant simulation. Three carrier band conditions were tested, each of which provided different amounts of pitch and periodicity information: 1) noise-band carriers for all speech segments; 2) pulse train carriers for voiced speech segments, in which the rate followed the fundamental frequency (F0) of the speech signal; 3) fixed-rate (150 Hz) pulse train carriers for voiced speech segments. The noise-band carriers preserved little pitch and periodicity information, as all temporal cues were limited by the 50 Hz temporal envelope extracted from each frequency band. The F0-controlled pulse train carriers preserved all pitch and periodicity information. The fixed-rate pulse train carriers preserved periodicity information, but no pitch information. Results showed that different carriers produced significantly different amounts of Chinese speech recognition, with the F0-controlled pulse train carriers producing the best performance. These results reflect the need to deliver adequate amounts of both pitch and periodicity information to Chinese-speaking cochlear implant patients.