In most speech sounds, and in all of those that occur in Spanish, the basic source of power is air being pushed out from the lungs, up through the windpipe (trachea) and eventually out of the mouth or the nose (or both). Depending on the type of sound being produced, the airstream is affected at various points in its passage from lungs to exit point by the shape, position or activity of the organs that lie in its path. It is these disturbances that give speech sounds their characteristic properties and, consequently, most speech sounds are classified in terms of the organs involved in their production. It is important, therefore, to be very familiar with the topography of the throat and mouth, which together form the oral tract. The principal points of reference are shown in Figure 1.
The alveolar ridge is the promontory that curves across the roof of the mouth just behind the upper front teeth and which can be felt with the tip of the tongue. The palate, or hard palate, is the dome-like structure that lies behind the alveolar ridge. The velum, or soft palate, lies immediately behind the palate – most people can reach it with the their tongue if they run the latter’s tip over the palate in the direction of the back of the mouth. The uvula, as its name implies, is a small grape-like organ that hangs from the lower end of the velum.
Much further back can be found the larynx, a cartilaginous organ containing two small muscular folds. The latter items are the vocal cords and the gap between them is known as the glottis. The larynx's position can be easily identified, because part of it, the thyroid cartilage, is externally observable. This is the Adam’s apple. The pharynx is essentially a tube that connects the back of the mouth to the larynx.
The tongue – a formless muscle – is of particular importance in the production of speech sounds, and you normally have to refer to a specific part of it when you classify a speech sound. The parts normally referred to are shown in Figure 2.
Figure 2 The principal points on the tongue