Relating automatic vowel space estimates to talker intelligibility

Differences in pronunciation have been shown to underlie significant talker-dependent intelligibility differences. There are several dimensions of variability that are correlated with talker intelligibility including pitch range, vowel-space expansion, and rhythmic patterns. Prior work has shown that some of the better predictors of individual intelligibility are based on the talker’s F1 by F2 vowel space, but findings are based on handcorrected measurements on carefully balanced sets of vowels, making large scale analysis impractical. This paper proposes a novel method for automatic estimation of a talker’s vowel space using sparse expanded vowel space representations, including an approximate convex hull sampling, which are projected to a low dimensional space for intelligibility scoring. Both supervised and unsupervised mappings are used to generate an intelligibility score. Automatic intelligibility rankings are assessed in terms of correlation with an intelligibility score based on human transcription accuracy. We find that including a larger sample of vowels (beyond point vowels) leads to improved performance, obtaining correlations of roughly 0.6 for this feature alone, which is a strong result given that there are other factors that may also contribute to a talker’s intelligibility in addition to a talker’s vowel space area.