Acoustical Consequences of Lip, Tongue, Jaw, and Larynx Movement

An articulatory model is presented. It defines a procedure for deriving a set of formant frequencies from information on the state of the lip muscles, the position of the jaw, the shape and position of the tongue body, and larynx height. The acoustic and auditory consequences of varying these parameters individually are reported. The introduction of the jaw as a separate parameter—a feature not used in previous articulatory models—makes it possible to explain why “openness” occurs as a universal phonetic feature of vowel production. According to the explanation proposed, the degree of opening of a vowel corresponds to a position of the jaw that is optimized in the sense that it cooperates with the tongue in producing the desired area function. Such cooperation prevents excessive tongue shape deformation. Our results suggest that, in order to reflect this principle of articulatory synergism, “tongue height,” although primary with respect to its acoustic consequences, should be represented as a derived feature characteristic of the final vocal-tract configuration.