Speech Production

Overview

Sounds are made by compression of the lung volume in respiration which forms an air flow. This is only audible if it vibrates the vocal folds of the larynx (phonation). These sounds can then form speech by modifications which take place in the supralaryngeal vocal tract, called articulation.

1)      Respiration

During  exhalation the lung volume is increased since the rib cage expands and the diaphragm is lowered. An increase in volume means that the pressure in the lungs is lowered below the atmospheric pressure, so air is drawn into them. Then, the lung volume decreases as the rib cage contracts and the diaphragm is raised. As this happens the pressure in the lungs increases, so the air is expelled.

2)      Larynx

The larynx (commonly known as Adam’s Apple)  is located in the upper area of the throat, directly below the tongue. It is composed of a network of cartilages (the main ones are the arytenoid, cricoid and thyroid cartilages) which are connected by joints, membranes and ligaments. These vibrate and tilt which cause changes in the focal folds/ cords. These vocal folds stretch across the larynx and they separate the trachea and the pharynx when closed (however, breathing is not permitted when the vocal folds are closed). The opening between the focal cords is called the glottis. When the sub-glottal pressure is high, the vocal folds open but then spring back together elastically. The pressure will then build up again very fast and the same will happen.  This process is known as phonation and shows how ‘voiced’ sounds are produced.

3)      Articulators

Once the sound has been produced at the larynx, this can then be modified by changing the shape of the vocal tract above. An example of this is when the velum can be opened or closed by moving the tongue or jaw, which then opens the air flow into the nasal cavity of the oropharynx.