Examination of coarticulation features in Mandarin tone productions using locus equation

Abstract

Locus equation (LE) was designed to examine the spectral changes during coarticulated consonant‐vowel (CV) utterances through obtaining a regression straight‐line which fits to points on a 2‐D Cartesian coordinate system, with the ordinate and abscissa corresponding to onset F2 and target (mid‐vowel) F2, respectively [Lindblom (1963); Sussman et al. (1992)]. The linear LE functions, according to Sussman et al. (1991), were referred as potential “CV prototypes”, of which the slopes are considered to indicate the extent of coarticulation‐induced variation in a CV(C) context. This study attempts to investigate coarticulation features in Mandarin speech sounds by comparing LE among different Mandarin tones. A tonal language, specifically Mandarin, where a change in tone of a syllable leads to a change in lexical meaning, will be used in the study. There are four contrastive tones in the Mandarin, each of which is realized by vocal pitch variation in vowel segment. Based on recent findings of kinetic interrelations between phonatory and articulatory systems during Mandarin tone productions [Gao and Esling (2003)], this study intends to determine if coarticulation features in Mandarin CV contexts vary with variation of lexical tones at which each of the following vowel sounds is produced.