Computation of phonation aeroacoustics by an INS/PCE splitting method

In this study, an INS/PCE splitting method is exploited to compute vocal sound generated within the glottis by a pulsating air jet at maximum speed less than Mach number of 0.1. The acoustic field is computed by solving the perturbed compressible equations (PCE), with acoustic sources acquired from the transient hydrodynamic solutions obtained by the incompressible Navier-Stokes equations (INS). The governing equations are spatially discretized with a sixth-order compact scheme and time-integrated by a four-stage Runge-Kutta method. The computed results show that a voice quality is closely related to the vortical structure in the shear layer of the pulsating jet and the jet characteristics are determined by its local Reynolds number, pulsating frequency (or fundamental frequency), and glottis closure. It is also found that the rotational motion of the glottis controls the glottal impedance by changing the flow separation points between the leading- and trailing-edge of the vocal folds and this increases the mechanical efficiency of the glottis as a sound generator in the phonation process.