Experimental Study on Inspiratory Phonation Using Physical Model of the Vocal Folds

In inspiratory phonation, the air is inhaled from the mouth. The inhaled air passes through the glottis towards the lungs, thereby inducing the vocal fold vibrations. Such phonation takes place in various situations such as sighs, laughter, and crying. To characterize the inspiratory phonation, an experimental study was carried out using a physical model of the vocal folds. By reversing the direction of the airflow that passed through the vocal fold model, the inspiratory phonation was experimentally realized and compared with the normal expiratory phonation. Our experiments revealed that the phonation threshold pressures as well as the volume flow rates decreased under the inspiratory condition. Accordingly, the vocal efficiency was increased. The fundamental frequency was also increased under the inspiratory condition. The kymograms showed that phase of the upper edge of the vocal fold advanced that of the lower edge under the inspiratory phonation. A mathematical model of the vocal folds was further constructed to elucidate these experiments. Except for few aspects, our experimental findings are in good agreement with the preceding studies on inspiratory phonation (e.g., reversed propagation of the mucosal waves observed in a singer, increased pitches in human subjects, and use of inspiratory phonation in speech therapy).