The acoustic qualities of Bora vowels

Bora contains the vowel system /i e a o i w/, where /i/ is high, central, open, unrounded and /w/ is high, back, open, unrounded. A contrast between /i/ and /u/ is exceedingly rare in the languages of the world. An opposition between a central and a back vowel which are otherwise identical is theoretically significant since it shows that the binary feature [+/- back] is too weak to encode all phonological contrasts along the front/back dimension. However, previous analyses of languages containing such oppositions are based primarily on impressionistic transcriptions without instrumental confirmation. This study contributes to the debate by providing acoustic evidence supporting the minimal contrast between /i/ and /w/ in Bora. The results indicate that these phonemes have identical F1 values, but /i/ yields higher F2 and F3 measurements than /w/, in keeping with their reported difference in backness.