Investigation of the Vocal Fold Vibration from the Viewpoint of its Superficial Structure and Lubrication
Hiroyuki Fukuda, Shigeji Saito, Satoshi Kitahara, Nobuyuki Kokawa, Tadashi Ichikawa, Yutaka Isogai, Katsumi Makino, Tohoru Tsuzuki · The Japan Journal of Logopedics and Phoniatrics · 1981
It seeme most likely that the essential principle of the vocal fold vibration is a wave like motion of the membrane of the vocal fold itself. For easy travelling of the membrane, elasticity and viscosity which the vocal fold membrane has, are thought to be the most important. From the viewpoint of this idea, we have carried out two experimental studies. One is to observe the vibration from the tracheal side. In the experiment using an excised larynx, it is very difficult to observe the lower surface of the vocal fold while vibrating, because the tube which is used to send the air flow from the trachea obstructs the direct observation of the lower surface vibration.Hence, we separated the trachea and larynx completely and then made a room at the supraglottic side. Instead of sending the air flow from the trachea, we sucked the air from the supraglottic room. Thus we obtained the air flow from the subglottis to the supraglottis. In addition, we obtained a completely free space at the subglottic side in order to observe and photograph the vibration directly from the tracheal view.Remarkable vibrations are always obtained under any condition, at the upper surface of the vocal fold. It is very interesting that no closed phase is obtained at the lower surface vibration of an excised larynx and that the higher the pitch, the smaller the movement obtained at the lower surface vibration.The other is to study on the lubrication of the vocal fold during phonation. Dryness of the fold affects on the efficiency of of the phonatory function of the larynx. In addition, the quality of the mucous fluid is very important to obtain on adequate experimental phonation with reasonable air flow rate and subglottic pressure.From the facts mentioned above, it should be emphasized that from the viewpoint of phonodynamics, the vocal folds must have at least three layers, body, cover and mucous fluid layer.