Airstream Mechanism - Types of Airstream Mechanism

Types of Airstream Mechanism

Any of the three initiators − diaphragm, glottis or tongue − may act by either increasing pressure in the airstream or by reducing it with suction. These changes in pressure are often said to involve outward and inward airflow, and are therefore termed egressive and ingressive mechanisms; however, ingressive mechanisms often only reduce outward airflow.

Of these six possible airstream mechanisms, four are found in words around the world:

• pulmonic egressive, where the air is pushed out of the lungs by the ribs and diaphragm. All human languages employ such sounds (such as vowels), and nearly three out of four use them exclusively.
• glottalic egressive, where the air column is pushed upward by the glottis. Such consonants are called ejectives. Ejective and ejective-like consonants occur in 16% of the languages.
• glottalic ingressive, where the air column is rarefied as the glottis moves downward. Such consonants are called implosives. Implosive and implosive-like consonants occur in 13% of the world's languages.
• lingual ingressive, velaric ingressive, where the air in the mouth is rarefied by a downward movement of the tongue. These are the clicks. Clicks are regular sounds in ordinary words in fewer than 2% of the world's languages, all but one in Africa.

These mechanisms may be combined into airstream contours, such as clicks which release into ejectives.

The Khoisan languages have pulmonic, ejective, and click consonants, the Chadic languages have pulmonic, implosive, and ejective consonants, and the Nguni languages utilize all four, pulmonic, click, implosive, and ejective, in normal vocabulary.

In interjections, the other two mechanisms may be employed. For example, in countries as diverse as Canada, Sweden, Turkey, and Togo, a pulmonic ingressive ("gasped" or "inhaled") vowel is used for back-channeling or to express agreement, and in France a lingual egressive (a "spurt") is used to express dismissal. The only language where such sounds are known to be contrastive in normal vocabulary is the ritual language Damin; however, that language appears to have been intentionally designed to be different from normal speech.