Improving the voice pitch discrimination threshold through cochlear implants

Abstract

Aiming at the maximum use of linguistic information conveyed by the periodicity pitch of speech sound through cochlear implants, the possibility of improving the voice pitch discrimination threshold was examined for cochlear implantees: three acquired deaf adults and four congenitally deaf children. Female and male adult speech samples of vowel /a/ were analyzed and resynthesized using the STRAIGHT computer program to shift the original voice pitch (c1 and c) one octave upward and downward with a half‐step interval on the musical scale. By presenting those synthetic speech samples in pairs, the discrimination threshold of the voice pitch interval was observed. Association of the speech samples to the picture of a piano keyboard was helpful for conceptualizing the voice pitch change, especially for children. Preliminary observation results suggested that the discrimination threshold can be improved by less than one whole step by adults and two whole steps by children. Those figures were promising because, even for Japanese word accent and Chinese tones, which were conveyed by the precise changes in voice pitch, it was ascertained by acoustical analyses of both their production and perception that discrimination of a half‐step difference was small enough to recognize their pitch patterns.