Vortex shedding and the voice source

Abstract

The voice source is primarily an acoustic dipole produced by the fluctuating drag on the vocal folds [Zhao, Zhang, Frankel et al., J. Acoust. Soc. Am. 112, 2134–2146 (2002)]. In this paper the unsteady drag is determined theoretically in terms of the vorticity shed from the vocal folds. The principal source of acoustic energy is glottal-jet vorticity lying within an axial distance downstream of the glottis of less than about the glottal width. The vortex drag dipole is equivalent to the volume velocity source traditionally assumed to be located at the glottis. In addition, there exists a true, but weaker fluctuating volume source associated with volumetric changes of the vocal folds region. The relationship between the voice source dipole and sibilant fricative dipoles will be discussed. Our findings will be presented in a largely qualitative manner, so that the few equations used in the presentation can be understood physically. [Work partially supported by NIDCD-004688.]