Vocal closure patterns and source‐tract acoustic interaction

Abstract

For a strong or well‐carrying voice, glottal volume velocity waveforms obtained by inverse filtering are generally consistent with the hypothesis that an interaction between the time‐varying glottal impedance and an inertive component in the vocal tract impedance is causing an increase in the relative strength of higher harmonics and a decrease in average air flow. However, the required ratio of vocal tract inertance to glottal impedance is about a factor of 2 less than the greatest estimate that can be made from the glottal and vocal tract geometries using standard acoustic principles. The hypothesis that the unexplained difference is related to the shape of the vocal folds during the closing phase of their vibratory cycle was investigated by comparing glottal air flow and vocal fold contact area waveforms, with the latter obtained using an electroglottograph. To obtain an adequately accurate glottal airflow pulse and adequate synchronization of the recorded waveforms, the glottal flow waveshape was obtained by inverse filtering pharyngeal air pressure instead of the more commonly used radiated pressure or oral air flow. The transfer function of the required inverse filter is described, as well as problems and advantages of this procedure.