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Purpose: This investigation determined the strength of association between tongue kinematic and speech acoustic changes in response to speaking rate and loudness manipulations. Performance changes in the kinematic and acoustic domains were measured using two aspects of speech production presumably affecting speech clarity: phonetic specification and variability.
Method: Tongue movements for the vowels /ia/ were recorded in ten healthy adults during habitual, fast, slow and loud speech using three dimensional electromagnetic articulography. To determine articulatory-to-acoustic relations for phonetic specification, we correlated changes in lingual displacement with changes in acoustic vowel distance. To determine articulatory-toacoustic relations for phonetic variability, we correlated changes in lingual movement variability with changes in formant movement variability.
Results: A significant positive linear association was found for kinematic and acoustic specification, but not for kinematic and acoustic variability. Several significant speaking task effects were also observed.
Conclusion: Lingual displacement is a good predictor of acoustic vowel distance in healthy talkers. The weak association between kinematic and acoustic variability raises questions regarding the effects of articulatory variability on speech clarity and intelligibility, particularly in individuals with motor speech disorders.