Influences of auditory and vibrotactile information on vocal F0 responses

Feedback mechanisms for fundamental frequency (F0) control have been explored using the transformed auditory feedback (TAF) technique. However, those studies have underestimated the fact that the vibrotactile information from the laryngeal cavity wall during vocal-fold vibration is also involved in F0 control in speech. Our previous study examined the role of auditory and somatosensory information in vocalization. The present study further investigates how the vibrotactile information from the larynx influences vocal response parameters (F0, latency, and magnitude). Subjects participated in this experiment were instructed to sustain vowel /a/ while receiving the stimuli called the composite sine-wave modulation (CFM) of tone or vibration that shifts in frequency for a short period. The CFM signals were delivered through a bone-conduction speaker fixed on the neck surface near the larynx. Results demonstrated the larger magnitude, shorter latency and deeper peak F0 modulation in compensatory responses to the combined vibrotactile-auditory stimuli than to the responses to auditory-only stimuli. These findings strongly suggest that the vibrotactile afferent information is utilized in feedback control of F0 with the shorter delay to adjust vocal responses.