Nonlinear flow-structure coupling in a mechanical model of the vocal folds and the subglottal system.
Michael S. Howe, Richard S. McGowan · The Journal of the Acoustical Society of America · 2009
An analysis is made of the nonlinear interaction between flow in a mechanical model of the subglottal vocal tract and a model of the vocal folds. The mean flow through the system is produced by a “lung cavity” that is assumed to be steadily contracting. The lungs are connected to a subglottal tube of length L. The model for the vocal folds is at the other end of the subglottal tube. This model is a simple, self-exciting single-mass mathematical model of the vocal folds used to investigate the sound generated within the subglottal domain and the unsteady volume flux from the glottis. In the case when the absorption of sound by the lungs is presumed small and when the subglottal tube behaves as an open ended resonator (when L is as large as half the acoustic wavelength) a mild increase in volume flux is predicted. However, the strong appearance of second harmonics of the acoustic field is predicted at intermediate lengths, when L is roughly a quarter of the acoustic wavelength. In the cases of large lung damping, however, only modest changes in volume flux are predicted to appear. [Work supported by DC-009229 to UCLA under subcontract.]