A direct approach to the investigation of quasisteady approximation in phonation
Jong Beom Park, Luc Mongeau · The Journal of the Acoustical Society of America · 2003
Unsteady pulsating air jets through the human glottis are the main sound source in phonation. The quasisteady approximation has been frequently used for voice modeling. The time-varying air flow in the vocal tract is modeled using a sequence of comparable steady flows with the same wall position and boundary conditions as for the dynamically varying situation. Previous attempts to verify the quasisteady approximation used an indirect method, based on inverse filtering. In the present study, a direct method of comparing the orifice discharge coefficients of both dynamic and static jet flows was investigated. Time varying orifice coefficients of pulsating jets were derived from the measured instantaneous velocity field and orifice area, and then, compared to those of static configurations for the same orifice areas. It was found that dynamic orifice coefficients coincided with the static ones during closing rather than opening. Leading and trailing vortices of the pulsating jets were hypothesized as the main factor causing the dynamic transient effects.