All speech is made by setting a flow of air in motion, and then modifying its progress by superimposing on it some phonatory and articulatory configuration of the vocal organs. The purpose of this chapter is to describe the different ways in which such a flow of air can be made to move, either outwards from the body to the outside atmosphere, or inwards.

There are several different mechanisms for setting a sufficient volume of air in motion to allow audible speech to be produced by phonatory and articulatory modification of the airflow. By far the most common mechanism exploited by the languages of the world is the use of the respiratory system, to provide an outward-flowing stream of air which the larynx and supralaryngeal organs then modulate by phonatory and articulatory action. There are, however, two other mechanisms which are used in a number of different languages to provide the airflow for a usually rather limited number of sounds; one involves the larynx being used as a kind of piston, moving vertically in the cylinder of the pharynx; the other involves the tongue trapping a volume of air between the velum and some point further forward in the mouth.

Two important concepts in classifying the generation of airflow are firstly the identity of the organ that is operative in making the air move, and secondly, the direction of flow of the airstream that is thereby set into motion.