Phonetics Lab., Dept. of Linguistics, UCLA, Los Angeles, CA 90024-1543
Navajo is one of the comparatively few languages in the world in which there are said to be four vowel qualities, [i,e,(open aye),o]. Data from nine speakers of Navajo show that when the vowels are represented in terms of their formant frequencies, they are not approximately equidistant as predicted by Lindblom's dispersion hypothesis, in that [i] and [e] are too close together. What is also not predicted by this hypothesis is that the vowel [o] has a greater variance than the other vowels. There are two possible reasons for the greater variance of back vowels. On the one hand, considering the vowel space as a triangle, the high back corner could be less sharp than the high front or low back corners, allowing high back vowels to be in various locations that are all well dispersed from [(open aye)] and [i]. On the other hand, high back vowels could be less well defined in articulatory-acoustic terms; [i] and [(open aye)] are more in accord with Stevens' quantal hypothesis in that they have vocal tract shapes that can be somewhat varied while two formants remain close together, but there is no obvious high back quantal vowel.