Department of Linguistics
PHONETICS AND PHONOLOGY
Stricture is the extent to which the oral tract is constricted. The following diagram is ordered with the greatest "degree" (or "rank order") of stricture at the top and the least degree of stricture at the bottom. The greatest degree of stricture is the "stop" with complete closure or constriction of the oral cavity at some point.
Note that stricture specifically relates to oral cavity constriction and ignores the state of the nasal cavity (ie. whether the velum is open or closed).
Stricture types: Degree of closure as a function of time.
Stop and Tap Stricture
Stop stricture is complete closure followed by release. At the release of an oral stop there is a brief burst of noise which may be followed by a period of aspiration.
Note that tap stricture is really a special case of stop stricture. A tap is an extremely brief stop.
A trill consists of a series of taps interspersed by narrow openings of a similar cross-sectional area to a fricative.
Fricative stricture consists of a very narrow opening that has a small enough cross-sectional area to cause the air to flow turbulently. Turbulent air flow generates random or aperiodic sound that characterises fricatives.
Approximant stricture consists of a opening with a greater cross-sectional area than a fricative but the opening is narrower than that of a vowel. The opening is greater than that which would produce turbulent air flow and aperiodic noise.
This is stricture typical of vowels. Semi-vowels are also often produced with resonant stricture.