Tongue surface dynamics during speech and swallowing

Abstract

This investigation characterizes tongue surface dynamics that underlie phonemic variation and that distinguish speech from swallowing. Vertical displacements of pellets affixed to the tongue were extracted from the x-ray microbeam database [Westbury, J. X-ray Microbeam Speech Production Database Users Handbook, Version 1 (1994)], which contains articulatory kinematic data from 57 typical speakers. Participants recited 21 vowel–consonant–vowel (VCV) combinations, read the Grandfather Passage, and swallowed 10 cc of water. Consonantal context was manipulated in the VCV utterances as a means to describe the range of tongue dynamics produced during speech. For each task, tongue dynamics was quantified by performing zero-lag cross correlations on selected pellet pairs. A coupling index was then computed by scaling the derived coefficients by a multiplier that reflected the amplitude of each displacement signal. A wide range of movement coupling among tongue pellets was observed across tasks. Phonemic differentiation in vertical tongue dynamics was observed as coupling varied predictably across marker pairs with place of articulation. Moreover, tongue displacements for speech and swallowing clustered into distinct groups based on their coupling profiles. The strengths and weaknesses of the coupling index for characterizing tongue surface dynamics across multiple speakers are considered.