ABSTRACT
Phonation is of particular interest in physiology because it requires a close coordination between the movements of the respiratory bellows, the vocal cords, and the supralaryngeal structures. Movements of the respiratory bellows provide the subglottic pressure and the expiratory airflow needed to drive the sound generator and determine the loudness of the voice. Movements of the vocal cords produce sound by transforming the pressurized airstream from the lungs into a series of air pulses. Contraction of intrinsic and extrinsic laryngeal muscles regulates the length, tension, and mass of the vocal cords and affects the pitch of the voice. Finally, movements of the supralaryngeal structures (pharynx, soft palate, tongue, lips), by acting as resonators, influence the loudness of the voice and modify the sound to obtain recognizable phonemes. These different processes need to be tightly adjusted to produce intelligible speech while minimizing the interference with the respiratory function of the system. In this chapter, we will focus on the mechanical events responsible for the generation and the control of subglottic pressure during normal speech at conversational sound level. We will also describe some features of special phonatory tasks like singing or producing a single tone at constant pitch and loudness. Finally, we will discuss speech production in patients with neuromuscular diseases involving the respiratory muscles and in patients with stuttering speech.
