Neutralizing differences in jaw displacement for English vowels

Maximum jaw displacement in the syllable varies primarily by vowel quality, syllable position in the phrase, lexical and phrasal stress, prosodic conditions, and the syllable consonantal periphery. EMA recordings were made of CVC syllables in 3-word phrases uttered by an American English speaker, where three target CVC words occurred in phrase initial, middle, and final positions, in order to ascertain the effect of vowel quality and syllable phrase position on jaw displacement, independent of other factors. Eleven English vowels, omitting diphthongs, formed the syllable nuclei, voiceless obstruents /p, t, k/ formed the syllable periphery, and the intonation pattern was kept constant for each phrase. Jaw displacement was measured by coil placement at the midline of the base of the lower incisors. The maximum vertical mandibular displacement on the vertical axis (z-axis for 3D EMA) was measured for each target CVC word. For each of the 11 vowels, an algorithm was developed to neutralize differences in the contribution of the mandibular vertical excursion in each of the three phrasal positions, i.e., 33 neutralization measures. These results indicate that this method may neutralize the mandibular contribution to differences in phonological vowel quality and phrasal position.