Aerodynamic constraints on sound change: The case of syllabic sibilants

Abstract

High vowels are known to assimilate in place of articulation and frication to a preceding sibilant. Such an assimilation process is found in an historical sound change from Middle Chinese to Modern Mandarin (e.g., */si/ became [sz] ‘‘poetry’’). However, such assibilation is systematically absent when the vowel is followed by a nasal consonant. This paper investigates the co-occurrence restriction between nasalization and frication, demonstrating that pharyngeal pressure is so significantly vented during the opening of the velic valve that the necessary pressure buildup behind the constriction of a fricative is consequently severely diminished, resulting in no audible turbulence. It reports the aerodynamic effects of nasalization on vowels, as spoken by a native speaker of American English (presumed to parallel the phonetic conditions present in Middle Chinese). The results reveal that in comparison to oral vowels the pharyngeal pressure, volume velocity, and particle velocity decrease dramatically when high vowels are nasalized. Based on this study, a physical motivation for the phonological patterns with respect to the interaction between syllabic sibilants and nasal is advanced. [This work is supported by the President’s Undergraduate Fellowship 1997–1998.]