Estimating the nonacoustic fluctuating velocity amplitude from Cranen and Boves’ vowel production data

Abstract

In a dynamic mechanical model of the larynx and vocal tract [Barney et al., J. Acoust. Soc. Am. (in press)], the fluctuating velocity field was shown to have contributions from an acoustic disturbance and also from nonacoustic flow associated with vortex transport along the model tract. Nonacoustic velocity fluctuations, interacting with changes in the tract area function, can constitute significant sources of sound; in the vocal tract these could occur at the lips, teeth, etc. However, such additional sources of sound are not generally included in models of voiced speech production. Cranen and Boves [J. Acoust. Soc. Am. 77, 1543–1551 (1985)] obtained in-tract and radiated sound-pressure time histories from phonating subjects, from which they computed in-tract velocities. In this study the relative amplitudes of the acoustic and nonacoustic velocity fluctuations have also been estimated from their data. Though vocal tract area functions are not available, simple models of sound transmission and radiation allow an order-of-magnitude prediction of the contribution to the radiated sound associated with each part of the in-tract velocity field. Although these are preliminary investigations using a restricted data set, the evidence suggests that there is nonacoustic fluctuating flow within the vocal tract, capable of significant sound generation.