A Study of Human Vocal Fold Vibration by Means of Simultaneous Measurement of Subglottal Pressure and Glottal Velocity During Phonation(Mechanical Systems)

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, without this airflow, vocal folds cannot oscillate. The airflow in a larynx is a key factor in the vocal fold vibration. 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, direct measurement of subglottal pressure by means of a catheter pressure transducer, and simultaneous observation of vocal fold movement by means of a high-speed digital camera. During the closing phase of the glottis, the vocal folds constrict the airflow and the airflow velocity is at its highest. The subglottal pressure also becomes higher during the closing phase, however, the closing of the upper lips of the vocal folds is later than the moment the subglottal pressure is at its highest. The movement of the upper lips dose not synchronize with that of the lower lips. These are important because they provide crucial information to create better simulation models of the phonation mechanism.