Effects of identity-related voice cues on speech timing under delayed auditory feedback.

Delayed auditory feedback (DAF) disrupts speech timing, but whether this disruption depends on acoustic cues in the feedback voice remains unclear. Twelve Japanese male speakers read sentences while feedback was presented with actual delays of 30-40, 130-140, and 230-240 ms and with pitch shifting and/or spectral-envelope expansion/compression. Mixed-effects analyses treating pitch and spectral-envelope manipulations separately showed that utterance duration increased with delay and exhibited a significant delay-dependent effect of spectral-envelope manipulation, whereas pitch effects were not significant. Total mora count increased with delay without clear pitch- or spectral-envelope-related modulation, and mean mora duration also increased with delay.