*Air coming out of the lungs forms the basis of most speech sounds. A downward movement of the rib cage and/or an upward movement of the diaphragm forces the air out of the lungs, causing a pulmonic airstream.
*A glottalic airstream is caused by closing the glottis so that the air in the lungs is contained below the glottis. The air in the vocal tract forms a body of air that can be moved. Moving the closed glottis upward will force the air out of the mouth, whereas moving the closed glottis downward will cause the air to be sucked into the mouth. Stops made with a glottalic egressive (outward) airstream mechanism are called ejectives. Stops made with an ingressive (inward) glottalic airstream mechanism are called implosives.
* The velaric airstream mechanism is used in producing clicks, such as the click expressing disapproval ("tut-tut"). Clicks are stops made with an ingressive velaric airstream mechanism. For a dental click, there are both dental and velar closures, resulting in a trapping of air in between the two closures. A click is produced when the vacuum is released by lowering the tip of the tongue. If the vacuum is released by lowering the side of the tongue, a lateral click is produced, which is the sound used for encouraging horses.
Picture of the speech production system