The effects of physiological adjustments on the perceptual and acoustical characteristics of vibrato as a model of vocal tremor.

The purpose of this study was to investigate the effects of physiological adjustments on listeners' perception of the magnitude of modulation of voice and to determine the characteristics of the acoustical modulations that explained listeners' judgments. This research was carried out using singers producing vibrato as a model of vocal tremor. Twenty healthy adults participated in a perceptual study involving pair-comparisons of the magnitude of "shakiness" with singers' samples, which differed by fundamental frequency, vocal quality, and vowel. Results revealed that listeners perceived a higher magnitude of voice modulation when female samples had a pressed vocal quality. Acoustical analyses were performed with voice samples to determine the features that predicted listeners' judgments. Based on regression analyses, listeners' judgments were predicted to some extent by modulation information in frequency bands across the spectrum.