Analysis of Human Vocal Fold Vibration by Means of Glottal Velocity Measurement and High-Speed Imaging

Human voices originate from the vibration of vocal folds in the larynx. In most previous studies on voice generation, a planar sound source was assumed for a laryngeal sound source and the effects of airflow in a larynx were neglected. However, no direct in vivo measurement of human glottal velocity has been reported. Therefore, detailed study of this airflow is necessary to elucidate mechanisms of human phonation. In the present study, airflow just above the glottis was experimentally analyzed to clarify the phonation mechanism and seek better modeling of vocal folds. This experiment focused on direct measurement of the airflow velocity by means of a tiny hot-wire probe and simultaneous observation of vocal fold movement by means of a high-speed digital camera. Experimental results show that the periodic change in the airflow velocity occurs out of phase with the opening of the glottis, although both have the same fundamental frequency. This is important because it provides crucial information to create better simulation models of the phonation mechanism.