On the relation of apparent naturalness to phonetic perceptual identification

A set of synthetic test syllables was created varying in the attributes of apparent naturalness and phonetic place-of-articulation. These acoustic items were used in a new test of the relation of naturalness to phonetic perceptual resolution. An earlier study had found that variation in the form of the excitation of a formant pattern greatly affected impressions of naturalness while minimally affecting the resolution of the phonetic place. The present study assessed the relation of naturalness and intelligibility when the bandwidths of formant centers were varied. We conducted a naturalness tournament composed of items drawn from the test series; and, we assayed the sensitivity of perceivers to place contrasts by estimating the cumulative d’ across the series in identification tests. Unlike our prior observations, these new outcomes reveal both a narrower range of naturalness variation and a close relation in findings of the naturalness tournament and the measures of phonetic sensitivity. Together, this pair of studies shows that intelligibility and naturalness can be either orthogonal or contingent aspects of speech perception. These measures offer a tool to understand rule-based and exemplar-based components of phonetic perception. [Research supported by NIDCD.]