Acoustic measurements of the vocal-tract area function: sensitivity analysis and experiments

A method to determine the vocal-tract cross-sectional area function from acoustical measurements at the lips is analyzed here. Under the framework described by Sondhi and Gopinath (1971) and implemented by Sondhi and Resnick (1983), a sensitivity analysis of the vocal-tract area function, derived from the impedance or reflectance at the lips is performed. It indicates that, in the ideal case, the area function is not heavily affected by random distortions of the impulse response at the lips. Simulations and real measurements show that the method works relatively well, except for regions behind narrow constrictions. In this case, an excitation pulse with high energy, as well as a fine sampling, proved to be important. The excitation used here is a time stretched pulse. It produces an excitation with high energy without the necessity of a high power sound generator device.