Speech science

The production of speech is a highly complex motor task that involves approximately 100 orofacial, laryngeal, pharyngeal, and respiratory muscles.

During inspiration of air, the diaphragm contracts and the lungs expand drawn by pleurae through surface tension and negative pressure.

Forced inspiration for speech uses accessory muscles to elevate the rib cage and enlarge the thoracic cavity in the vertical and lateral dimensions.

If the volume of airflow is constant, the velocity of the flow will increase at the area of constriction and cause a decrease in pressure below once distributed.

In a third process of speech production, articulation, mobile and immobile structures of the face (articulators) adjust the shape of the mouth, pharynx and nasal cavities (vocal tract) as the vocal fold vibration sound passes through producing varying resonant frequencies.

[5][6] The seminal lesion studies of Paul Broca indicated that the production of speech relies on the functional integrity of the left inferior frontal gyrus.

Once in the middle ear, which consists of the malleus, the incus, and the stapes; the sounds are changed into mechanical energy.

Once inside the inner ear, the message is transferred into hydraulic energy by going through the cochlea, which is filled with fluid, and on to the Organ of Corti.

This organ again helps the sound to be transferred into a neural impulse that stimulates the auditory pathway and reaches the brain.

The motor theory is based upon the premise that speech sounds are encoded in the acoustic signal rather than enciphered in it.

The auditory theory puts greater emphasis on the sensory and filtering mechanisms of the listener and suggests that speech knowledge is a minor role that's only used in hard perceptual conditions.