airstream mechanism

A term used in PHONETICS for a physiological process which provides a source of energy capable of being used in SPEECH sound PRODUCTION. Air is moved inwards or outwards by the movement of this mechanism, producing respectively an INGRESSIVE and an EGRESSIVE airflow. The main initiator of air movement is the lungs (the PULMONIC airstream), which underlies the majority of human speech sounds. The ‘glottalic’ airstream mechanism, as its name suggests, uses the movement of the glottis (the aperture between the VOCAL FOLDS) as the source of energy (see GLOTTAL). The ‘velaric’ airstream mechanism, also as its name suggests, involves an airflow produced by a movement of the BACK of the TONGUE against the velum (see VELAR). It is also possible to start air vibrating using other movable parts of the vocal tract, such as the cheeks or the oesophagus, but these are not methods used in normal speech production. The use of the cheeks produces a ‘buccal’ voice (the basis for the Donald Duck effect); the ‘oesophageal’ voice is characteristic of the speech taught to people who have had their larynx surgically removed.