Sound generated by aerodynamic sources near a deformable body, with application to voiced speech

Abstract

An analysis is made of sound generation by aerodynamic sources near an acoustically compact body (or compact surface feature on a large boundary) that can deform in an arbitrary manner. It is shown how such problems can be investigated by simple extension of the compact Green's function used in the treatment of compact rigid bodies. It is known that this method can furnish rapid and accurate predictions of sound generated by flows with extensive, non-compact distributions of sources in cases where a numerical treatment requires at best tens or hundreds of hours of CPU time. Illustrative applications are made to study (i) the sound generated by a nominally rigid circular lamina of time-dependent radius held in an irrotational mean stream, and (ii) the production of voiced speech by vorticity interacting with a simple model of the vocal folds. In case (ii), it appears that predictions are represented well by a quasi-static approximation that permits the particular results of this paper and previous investigations to be generalized to arbitrarily configured folds.

Variability in the relationships among voice quality, harmonic amplitudes, open quotient, and glottal area waveform shape in sustained phonation

“…Because existing empirical data are not sufficient to clarify this situation, this study examined the relationship between H1*-H2* (measured from recorded acoustic signals), OQ, and the asymmetry coefficient (the length of the opening phase relative to the open phase, e.g., Henrich et al, 2001;Shue and Alwan, 2010), 2 measured synchronously from high-speed video images of the vibrating vocal folds. Note that previous work on this topic has used models of the glottal flow, which may differ in pulse skewness from the glottal area functions measured here (e.g., Howe and McGowan, 2007). However, these differences in skewness should not affect measures of OQ, which depend on glottal opening and closing instants, and not on precise pulse shapes.…”

On the acoustical relevance of supraglottal flow structures to low-frequency voice production

“…From the sound production point of view, on the one hand, these complex flow structures in the downstream glottal flow field are sound sources of quadrupole type (dipole type when obstacles present in the pathway of airflow) and radiate sound mostly at high frequencies (generally above 2 kHz) due to the small length scales associated with the flow structures (Zhang et al, 2002;Howe and McGowan, 2007). Therefore, these flow features have to be accurately modeled if the high-frequency component of voice is to be reproduced.…”

Source-tract interaction with prescribed vocal fold motion

“…Further, dissipation is confined to the lateral boundaries with strong shear layers and wall vibration. For such flows the vortex sound equation can be written (Howe, 1998(Howe, , 2002Howe and McGowan, 2007).…”