Changes in vocal tract resonance during a pitch cycle

Abstract

Vocal tract (VT) resonances during a pitch cycle were examined using area functions of the five Japanese vowels extracted from MRI data of a male subject. The volume-velocity distribution within the VT at each formant was calculated by a transmission line model, as a function of the glottal area. Our previous study showed that in glottal closure condition the fourth formant was provided by the laryngeal cavity (LC) and the other formants by the VT excluding LC, the VT proper (VTp). During the early stage of glottal opening, the fourth formant disappeared, as it had been provided by the closed-tube resonance of LC. After glottal opening, the single volume-velocity node of the first formant moved to the middle pharynx, shortening the effective VT length and thus increasing its frequency. At the other formants, a node appeared at the junction between LC and VTp, and the VT resonance during the glottal opening condition could therefore be approximated by the VTp. This result indicates that the VTp was responsible for most of the VT resonances throughout a period, while LC provided the fourth formant in the glottal closure period. [Work supported by NICT and MEXT KAKENHI of Japan.]