LOCUS EQUATIONS IN THE LIGHT OF ARTICULATORY MODELING

This paper examines the significance of the so-called ''locus equation '' by means of articulatory simulations of V1CV2 utterances with diffe rent intergestural timing, and, therefore, with varying degrees of con sonant-vowel coarticulation. Movement toward the vowel V-2 started (i) at the beginning of the transition to the consonant, (ii) at the begi nning of the complete consonant closure, or (iii) at the beginning of the release of the consonant. For each combination of vowels and each consonant, F-2onset of V-2 as a function of F-2 of V-2 was adequately described by straight lines corresponding to locus equations (referred to as first-order locus equations). The findings show that the derive d locus equations depend on the consonant place on the one hand and on the degree of coarticulation on the other. The effect of varying inte rgestural timing was compared with published data on locus equation co efficients for individual speakers using the format of y-intercept plo tted versus slope for each place of articulation (referred to as a sec ond-order locus equation). These comparisons demonstrate that the mode l adequately captures the natural place-dependent variations in slope and intercept. Also it provides accurate numerical matches with their speaker-specific ranges suggesting the hypothesis that the variability derives, to a significant extent, from individual differences in inte rgestural timing. (C) 1997 Acoustical Society of America. [S0001-4966( 97)01910-3] PACS numbers: 43.70.Bk [AL].