What is good... LANGUAGE

To simplify the anatomy required for human speech by using an analogy, think of a small tube resting inside a larger tube (see Figure 3). The inner tube consists of the trachea going down to the lungs, and the larynx (which houses the voice box). At the larynx, the inner tube opens out to the larger tube, which is known as the pharynx. It not only carries sound up to the mouth, but it also carries food and water from the mouth down to the stomach. A rather simplistic description of how humans utter sounds in speech can be characterized by the control of air generated by the lungs, flowing through the vocal tract, vibrating over the vocal cord, filtered by facial muscle activity, and released out of the mouth and nose. Just as sound is generated from blowing air across the narrow mouth of a bottle, air is passed over the vocal cords, which can be tightened or relaxed to produce various resonances.

The physiological components necessary can be divided into: (1) supralaryngeal vocal tract; (2) larynx; and (3) subglottal system (see Figure 4). In 1848, Johannes Muller demonstrated that human speech involved the modulation of acoustic energy by the airway above the larynx (referred to as the supralaryngeal tract). Sound energy for speech is generated in the larynx at the vocal folds. The subglottal system—which consists of the lungs, trachea, and their associated muscles—provides the necessary power for speech production. The lungs produce the initial air pressure that is essential for the speech signal; the pharyngeal cavity, oral cavity, and nasal cavity shape the final output sound that is perceived as speech. This is the primary anatomy used in common speech, aside from those sounds produced by varying the air pressure in the pharynx or constricting parts of the oral cavity.