THE SPEECH MECHANISM. THE PRODUCTION OF SPEECH SOUNDS

Sound is produced when air is set into motion. The speech production mechanism consists of an air supply, a sound source, which sets the air into motion, and a set of filters that modify the sound in different ways. The air supply is provided by lungs. The sound source is the larynx where the vocal cords are located. The filters are the organs above the larynx: the tube of the throat between the larynx and the oral cavity which is called pharynx, the oral cavity and the nasal cavity. These passages are collectively known as the vocal tract.

(The diagram shows a side view of the parts of the vocal tract which is important to recognize when we want to understand how speech sounds are produced).

The air released by the lungs comes through the wind-pipe and arrives first at the larynx. This is a boxlike part in the throat which contains two small bands of elastic tissue, that lie opposite each other across the air passage. These are the VOCAL CORDS. They can be pulled together or drawn apart. The opening between the cords is called GLOTTIS. As air passes through the glottis, different glottis states are produced, depending on the positioning of the vocal cords. Four important states of glottis are:

The vocal cords are wide apart. Sounds produced in this position are called VOICELESS.

Narrow glottis. The air passage is narrowed, thus fricative /h/ sound is produced.

Position for the vocal cords vibration. The edges of the vocal cords are touching each other. Air passing from the lungs in regular puffs through the glottis will cause vibration which is, in fact, a regular and very rapid opening and closing of the vocal cords. Thus voiced consonants and vowels are produced.

Vocal cords tightly closed.(It’s a position for holding breath, also called GLOTTAL STOP). Examples: BLACK CAT /blæk kæt/, NOT NOW /nɒt naʊ/

In the larynx the vocal cords set up vibrations of the airflow. The vibrating air passes through the filters (further cavities with passive and active articulators) which modify it into sounds. Passive (immobile) articulators are the hard palate, the alveolar ridge and the upper teeth. The active (mobile) articulators are the pharynx, the velum (or soft palate), the jaw, the lower teeth, the lips and, above all, the tongue. ARTICULATION is all the positions and movements of the speech organs necessary to produce a speech sound. Different vowels are produced by varying the shape of the mouth, using the tongue and lips. When in the pharynx, the mouth, and the nasal cavity there is an obstruction to the air-flow, a consonant is produced.

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