Aerodynamic sound of a body in arbitrary, deformable motion, with application to phonation

The method of tailored Greenʹs functions advocated by Doak [Acoustic radiation from a turbulent fluid containing foreign bodies, Proceedings of the Royal Society A 254 (1960) 129–145] for the solution of aeroacoustic problems is used to analyse the contribution of the mucosal wave to self-sustained modulation of air flow through the glottis during the production of voiced speech. The amplitude and phase of the aerodynamic surface force that maintains vocal fold vibration are governed by flow separation from the region of minimum cross-sectional area of the glottis, which moves back and forth along its effective length accompanying the mucosal wave peak. The correct phasing is achieved by asymmetric motion of this peak during the opening and closing phases of the glottis. Limit cycle calculations using experimental data of Berry et al. [High-speed digital imaging of the medial surface of the vocal folds, Journal of the Acoustical Society of America110 (2001) 2539–2547] obtained using an excised canine hemilarynx indicate that the mechanism is robust enough to sustain oscillations over a wide range of voicing conditions.