On the relation of apparent naturalness to phonetic perceptual resolution of consonant manner

How does the qualitative experience of speech influence phonetic perception? Our perceptual studies of consonant place and voicing have revealed a dichotomous relation between phonetic sensitivity and naturalness. Auditory quality and phonetic sensitivity sometimes co-vary, while in other conditions phonetic sensitivity is indifferent to huge variation in naturalness. New tests are reported extending the research to the dimension of manner, a contrast correlated with qualitatively distinct acoustic constituents in normal production. Speech synthesis techniques were used to create naturalness variants through (1) variation in the excitation of a synthetic voicing source and (2) variation in the bandwidth of the formant centers. Listeners calibrated the relative naturalness of items drawn from the test series, and the acuity of perceivers to the contrast between fricative and stop manner was estimated with cumulative d′ across the series in identification tests. Combined with our prior findings, these new tests show how intelligibility and naturalness can be either perceptually orthogonal or contingent aspects of consonant dimensions, offering a tool to understand normative functions in speech perception. [Research supported by NIH (DC00308).]