quantum (n.)

In PHONETICS, a term sometimes used for an anatomical region within which relatively large variations in ARTICULATION have no or minor ACOUSTIC consequences. However, a small shift outside of this zone will produce a large acoustic change. For example, when a CONSTRICTION reaches a critical cross-sectional area, there is a sudden shift as the sound moves from an APPROXIMANT to a FRICATIVE mode of articulation. It is argued that articulation is evolutionarily organized to make maximum use of the vocal tract’s ability to produce such changes, which are thus critical in the development of PHONOLOGICAL DISTINCTIVENESS. The notion is central to the quantal theory of speech proposed by US phonetician Kenneth N. Stevens (b. 1924). In a development of this approach, quantal relationships are proposed both between articulation and acoustics and also between acoustics and perception.