ASA 125th Meeting Ottawa 1993 May

2aSP3. The quasi-steady approximation, boundary-layer separation, and vibrations in the vocal tract.

R. S. McGowan

Haskins Labs., 270 Crown St., New Haven, CT 06511

Studies of voice and other flow-induced vibratory phenomena in the vocal tract often rely on the quasi-steady approximation based on the smallness of the Strouhal number (a nondimensional frequency measure). However, the relevant parameter do decide the application of the quasi-steady approximation to boundary-layer separation in oscillatory flow situations is a function of both the Strouhal number and the Reynolds number. Boundary-layer separation is important because it helps to determine the pressure distribution on the vibrating solid surface. Thus, unsteadiness in separation could provide a mechanism for energy exchange between the solid and the air to account for self-sustained oscillation. Such a mechanism will be illustrated by a model for tongue-tip trills. [Supported by NIH Grant Nos. DC-00121, DC-00865, and DC-01247 to Haskins Laboratories.]