The devoicing of /z/ in American English: effects of local and prosodic context

Abstract

Voiced fricatives are often taken as an example of sound that is ‘difficult’ to produce. It might therefore be expected that speakers would choose to simplify them. In English, the most common simplification is devoicing, especially for voiced sibilants. The nature of this process was examined in productions of /z/ and /s/ by four speakers of American English. These were recorded in matched word and phrase positions using acoustic, airflow, and electroglottographic (EGG) data. Although many tokens of /z/ showed little or no vocal fold vibration in the EGG signal, durational and aerodynamic differences maintained the distinction between /z/ and /s/. The speakers varied in overall frequency of devoicing, but showed similar rank orderings for frequency of devoicing in different contexts. Devoicing was most frequent in two kinds of environments: those where it could be viewed as assimilation to an adjacent voiceless context, and those where articulatory and aerodynamic effort tends to be reduced. These contexts (unstressed syllables, and ends of words or phrases) have been shown to favor other kinds of prosodically-structured lenition.