Direct determination of vocal tract wall impedance

The side wall of the human vocal tract yields and vibrates in response to contained sound pressure. This motion influences the acoustic resonances of the vocal tract and the vibratory behavior of the vocal cords. Accurate computer modeling of the cord/tract system therefore requires knowledge of the mechanical impedance of the yielding walls. Heretofore this factor has only been estimated indirectly from sound wave measurements. We describe here a technique for direct measurement of the wall impedance. We also give a rationale for interpreting the low-frequency impedance in terms of a simple mass, compliance, viscous-loss combination. Finally, we give mechanical parameters for the vocal-tract wall which we presently use in computer simulations.