Effects of bite block speech on intrinsic segment duration

The fact that low vowels tend to have longer intrinsic duration than high vowels is sometimes attributed to mechanical characteristics associated with the greater distance the jaw travels in producing low vowels. To investigate this tendency, 6 adult speakers of English each produced 72 [h]-vowel-consonant stimuli containing high and low vowels under 'normal' conditions and with their jaw fixed. If duration differences commonly observed between high and low vowels are a result of only mechanical effects of mandibular movement, it was hypothesized that stabilizing the jaw would eliminate these intrinsic vowel duration differences. Based on acoustic measurements that were made, it was found that the fixed-jaw conditions affected the intrinsic durational differences between high and low vowels to some extent, but the contrast was not entirely removed. In addition to the vowel duration changes, a number of systematic effects upon consonant closure duration were also observed as a result of the normal versus fixed-jaw conditions.