Effects of False Vocal Folds on Intraglottal Velocity Fields

Previous models have theorized that, during phonation, skewing of the glottal waveform (which is correlated with acoustic intensity) occurred because of inertance of the vocal tract. Later, we reported that skewing of the flow rate waveform can occur without the presence of a vocal tract in an excised canine larynx. We hypothesized that in the absence of a vocal tract, the skewing formed when dynamic pressures acted on the glottal wall during the closing phase; such pressures were greatly affected by formation of intraglottal vortices. In this study, we aim to identify how changes in false vocal folds constriction can affect the acoustics and intraglottal flow dynamics. The intraglottal flow measurements were made using particle image velocimetry in an excised canine larynx where a vocal tract model was placed above the larynx and the constriction between the false vocal folds was varied. Our results show that for similar values of subglottal pressures, the skewing of the glottal waveform, strength of the intraglottal vortices, and acoustic energy increased as the constriction between the false vocal folds was increased. These preliminary findings suggest that acoustic intensity during phonation can be increased by the addition of a vocal tract with false fold constriction.