Dynamic consequences of differences in male and female vocal tract dimensions.

Phonetic differences between male and female speakers are generally considered in terms of the static acoustic and perceptual consequences of different articulatory dimensions. This article investigates the dynamic acoustic and articulatory implications of differences in mean male and female vocal tract dimensions. The temporal acoustic consequences of time-varying twin-tube resonators of different dimensions are explored, and the possible implications for human speech production are considered. Empirical support for the theoretical predictions is sought by investigating the kinematic and acoustic patterns in diphthong productions from 26 female and 22 male speakers in the University of Wisconsin X-ray Microbeam Speech Production Database. Aside from expected acoustic differences, the shape of male and female formant tracks plotted in Bark space is found to be very similar. Male and female patterns of tongue movement, however, are found to be very dissimilar. The mean male diphthong, defined by the tracks of four midsagittal pellets, is characterized by greater pellet excursions, higher pellet speed, and consistently larger dorso-palatal strictures than its female counterpart. The empirical findings suggest that gender-specific dynamic behavior could be an important factor in accounting for nonuniform vowel system differences, but at the same time having more wide-ranging implications for transitional phenomena and undershoot.