Nasal Coda Loss in the Chengdu Dialect of Mandarin: Evidence from RT-MRI

Abstract

In the Chengdu Dialect of Mandarin, the /(V)an/ rime words have been described to have undergone a nasal loss process in the last decades. However, no acoustical or physiological evidence has been provided so far. In this study, we investigate this sound change process by directly looking at the velum gesture in the target segments from 4 Chengdu speakers. By means of real-time Magnetic Resonance Imaging (rt-MRI), the velum opening signal was captured along with synchronized and noise suppressed audio. The maximum degree of velum opening was compared between tautosyllabic and heterosyllabic VN sequences for different vowels (N = /n, ŋ/). Nasal consonant loss was most evident for tautosyllabic /(V)an/ rime words. This sound change, together with the observed diachronic vowel raising in /(V)an/ rimes, is compatible with other research showing a preference for low vowel raising before nasal consonants. This phonetically motivated oral vowel, which is a con-sequence of nasal coda loss and vowel raising, would form a new phonological contrast in this dialect e.g., from /pa, pan/ to /pa, pɛ/.