Articulatory and acoustic bases of locus equations

Articulatory factors underlying locus equations (LE:s) are investigated by means of an updated version of the APEX articulatory model. The modeling is focused on the determinants of LE linearity, slopes and intercepts. Linearity: For [b] and [d], linearity derives in part from acoustic mapping. In part tight linear clustering is enhanced by coarticulatory overlap. For [g], place of closure varies with vowel context along a front-back dimension. Acoustically, this translates into a relation between F2(onset) and F2(vowel) that is non-linear and is best described by two LE:s. Slopes/intercepts: In [b] and [d] variations in tongue body shape have a significant effect on F2 onsets. Thus, degree of coarticulation is a major determinant of LE slopes and intercepts. In contrast, in [gV], degree of coarticulation would be expected to affect LE parameters to a lesser degree.