Changes in voice-onset time in speakers with cochlear implants

Abstract

Voice-onset time (VOT) was measured for the English plosives in /Copen aye/ context spoken by three female and one male postlingually deafened recipients of multi-channel (Ineraid) cochlear implants. Recordings were made of their speech before activation of their speech processors and at intervals after activation, extending over several years. Also measured were: instantaneous oral airflow; sound pressure level; an indirect index of glottal aperture; and average airflow during passage readings. Pre-implant, all four speakers characteristically uttered plosives with too-short VOT, compared to normative data. After activation of their processors, all four were relatively accurate in identifying plosives with respect to voicing, and the three female speakers lengthened VOT. The women also increased glottal aperture post-activation. However, none of the women increased peak oral flow following plosive release, possibly because of a countervailing decrease in subglottal pressure: all three reduced SPL post-activation. Complementary results were found for the male speaker: a decrease in inferred glottal aperture and an increase in oral flow accompanied by an increase in SPL. Increases in glottal aperture are expected to inhibit the onset of voicing in the plosives [K. Stevens, Phonetica 34, 264–279 (1977)]. Consequently, some or all of the observed increases in VOT with activation of the implant processors may be due to ‘‘postural’’ adjustments of the larynx. [Work supported by N.I.D.C.D.]