Articulatory phonetics is concerned with describing speech sounds in terms of the positions of the vocal organs when producing any given sound. First, we briefly describe how speech sounds are produced.
In nearly all speech sounds, the basic source of power is the respiratory system pushing air out of the lungs. Air from the lungs goes up the windpipe and into the larynx at which point it must pass between two small muscular folds called the vocal cords. If the vocal cords are apart, the air from the lungs have a relatively free passage into the pharynx and the mouth. But if the vocal cords are adjusted so that there is only a narrow passage between them, the airstream causes them to vibrate. Sounds produced when the vocal cords are vibrating are so-called voiced sounds, as opposed to those in which the vocal cords are apart, which are said to be unvoiced sounds[14].
The air passages above the larynx are known as the vocal tract, and the shape of the vocal tract is a very important factor in the production of speech. Also, depending on the positions of the various articulators (i.e., jaw, tongue, velum, lips, mouth), different sounds are produced. Speech is produced as a sequence of sounds. Hence the state of the vocal cords, as well as the positions, shapes, and sizes of the various articulators, changes over time in relation to the sound being produced[14].
