TURBULENT NOISE IN DYSPHONIA

Turbulent noise is generated at the glottal chink when the speed of air flow through the chink exceeds a certain value, that is, the critical Reynolds' number. The present experiment with the use of a hard life-size model of the larynx demonstrated that the sound pressure of the turbulent noise increases in proportion to the square of the air flow rate for a glottal condition kept unchanged. If the flow-rate is maintained constant, the more intense noise is produced with a narrower glottal chink. The critical Reynolds' number for the laryngeal model was approximately 2,000. An obstacle hanging over the glottis enhances the generation of noise near the glottis. A rough-surfaced obstacle increases the noise level more markedly than a smooth-surfaced one does, although the difference is not great, within several decibels. If the amplitude of vibration of the vocal cord is extremely small, the intensity of the noise generated at the glottis can be presumed from the size of the glottal chink and the air flow rate.