Speech sound is a wave of air that originates from complex actions of the human body, which are supported by three functional units: generation of air pressure, regulation of vibrations, and control of resonators. The lung air pressure for speech results from accessory functions of the respiratory system during a prolonged phase of expiration after a short inhalation. Vibrations of air for voiced sounds are introduced by the vocal folds in the larynx: they are controlled by a set of laryngealmuscles and airflow from the lungs. The oscillations of the vocal folds convert the expiratory air into intermittent airflow pulses that result in a buzzing sound. The narrow constrictions of the airway along the tract above the larynx also generate transient source sounds: their pressure gives rise to air stream with turbulence or burst noises. The resonators are formed in the upper respiratory tract by the pharyngeal, oral, and nasal cavities. These cavities act as resonance chambers to transform the laryngeal buzz or turbulence noises into the sounds with special linguistic qualities. The main articulators are the tongue, lower jaw, lips, and velum. They generate patterned movements to alter the resonance characteristics of the supra-laryngeal airway. In this chapter, contemporary views on phonatory and articulatory mechanisms are summarized to illustrate the physiological processes of speech production, with brief notes on their observation techniques.
