Auditory-Motor Control of Fundamental Frequency in Vocal Vibrato

Abstract

Purpose: The purpose of this study was to investigate how classically trained singers use their auditory feedback to control fundamental frequency (f_o) during production of vocal vibrato. Two main questions were addressed: (1) Do singers produce reflexive f_oresponses to sudden perturbation of the f_o of their auditory feedback during production of vibrato indicative of feedback control? (2) Do singers produce adaptive f_oresponses to repeated perturbation of the f_o of their auditory feedback during production of vibrato indicative of feedback and feedforward control? In addition, one methodological question was addressed to determine if adaptive f_o responses were more precisely assessed with or without an auditory cue for f_o during the repeated f_o perturbation paradigm.

Method: Ten classically trained singers produced sustained vowels with vibrato while the f_o and harmonics of their auditory feedback were suddenly perturbed by 100 cents to assess reflexive control or repeatedly perturbed by 100 cents to assess adaptive control. Half of the participants completed the repeated perturbation experiment with an auditory cue for f_o, and the other half completed the experiment without an auditory cue for f_o. Acoustical analyses measured changes in mean f_o in response to the auditory feedback perturbations.

Results: On average, participants produced compensatory responses to both sudden and repeated perturbation of the f_o of their auditory feedback. The magnitude of the responses to repeated perturbations was larger than the responses to sudden perturbations. Responses were also larger in the cued, repeated f_o perturbation experiment than in the uncued, repeated f_o perturbation experiment.

Conclusions: These findings indicate that classically-trained singers use both feedforward and feedback mechanisms to control their average f_o during production of vibrato. When compared to prior studies of singers producing a steady voice, the reflexive f_o responses were larger in the current study, which may indicate that the feedback control system is engaged more during production of vibrato.

Keywords: Auditory-motor control; Fundamental frequency; Vocal vibrato.