Neutralizing differences in mandible displacement for English vowels

Maximum mandible 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 each target CVC word occurred in phrase initial, middle and final position, in order to ascertain the effect of vowel quality and phrase position on mandible displacement in the vertical plane, independent of other factors. Eleven English vowels formed the syllable nuclei, voiceless stops //p, t, k// formed the syllable periphery, and the intonation pattern was kept constant for each phrase. Mandible displacement was measured by coil placement at the midline of the base of the lower incisors. The maximum 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 the differences in the contribution of mandibular vertical excursion in each of the three phrasal positions. These results indicate that this method may neutralize the vertical mandibular contribution to differences in phonological vowel quality in different phrasal positions.