Temporal characteristics of vowel articulation: Electromyographic investigation of the “articulatory period”

Abstract

In speech, articulator movement precedes the acoustic signal [e.g., Meyer (1991); Gracco (1988); Lubker and Gay (1982); Bell-Berti and Harris (1981)]. The onset and offset of movement, i.e., the ‘articulatory period' (Bell-Berti and Harris, 1981, p. 13) is said to encompass the acoustic signal however the precise timing and variability of this period are not well understood. Using electromyography (EMG), we examine the onset/offset of the articulatory period as a function of phonetic context. We recorded EMG activity from the posterior and anterior regions of the genioglossus (GG) muscle of the tongue in subjects during the articulation of static vowels, static vowels with initial coronal or palatal fricatives and vowels embedded in the nonce word [∫pVp]. We show front and high vowels entail earlier onset of GG activation and that vowels preceded by coronal fricatives are associated with significantly earlier muscle activation than vowels preceded by palatal fricatives. We also note timing differences between GG regions. Thus, for these stimuli, posterior GG EMG activation encompasses the duration of anterior GG EMG activation. These findings underscore the dynamic nature of lingual movement wherein regional tongue muscle activities exhibit predictable differences determined in large part by phonetic context.