Mechanism of Phonation

Abstract

The sounds of speech are produced by the exhaled air from the lungs associated with changes of the true vocal cords to produce phonation. Further, exhaled air undergoes modifications in the “vocal tract”—the spaces and passages above the larynx—so that noises such as bursts and hisses produce the voiceless aspects of speech. The larynx functions in phonation by delicately adjusting the vocal cords to produce the required frequencies for the required length of time. It is important in the voiceless aspects of speech in a passive sense to ensure that the vocal cords are wide open at the glottis, so that air can easily pass out. The posterior cricoarytenoid muscles (the sole abductors of the vocal cords) are the specific agents also in inspiration by providing a wide-open glottis so that air can liberally enter the lungs prior to the exhalatory action required in both forms of speech.