Anatomy and Physiology

One of the functions of respiration is powering of the speech production mechanism.It provides energy source for oral communication.When the volume of the chest cavity increases/expands, air is inhaled into the lungs by the way of either the mouth or nose and trachea.An increase in the volume of the chest may be affected through a downward, contracting movement of the diaphragm; through an upward, outward movement of the lower ribs; or through a combination of both.The volume of the chest cavity increases as the air pressure decreases or the volume of the chest cavity decreases as the air pressure increases (Boyle's Law).In breathing for ordinary life processes, the periods of inhalation and exhalation are approximately equal.Breathing for speech, however, usually requires a longer period of exhalation than that of inhalation.Manner of production refers to the way the speech mechanism modifies the voiced or voiceless air stream.For voiced sounds, the vocal cords are held together by the action of the arytenoid cartilages, but they are held together less tightly than for a glottal stop.When air is forced up the trachea from the lungs, at a certain pressure it is able to force its way through the vocal folds, pushing them open.As air passes through the glottis, the air pressure in the glottis falls, because when a gas or liquid runs through a constricted passage, its velocity increases.This increase in velocity results in a drop in pressure of that gas or liquid (The Bernoulli Principle).Because of the drop in pressure, the vocal folds snap together, at the lower edgefirst, closing again.We perceive variations in the overall rate of vibration as changes in the pitch of the voice.For unvoiced sounds the vocal folds are abducted.Air can flow between them without being obstructed, so that no noise is produced by the larynx.If there is a sufficiently high rate of airflow through the open glottis, a qui…

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