Running title: Speech reference frames Does the speech motor control system utilize invariant vocal tract shape targets of any kind when producing phonemes? We present a four-part theoretical treatment favoring models whose only invariant targets are auditory perceptual targets over models that posit invariant constriction targets. When combined with earlier theoretical and experimental results (Guenther, 1995a,b; Perkell et al., 1993; Savariaux et al., 1995a,b), our hypothesis is that, for vowels and semi-vowels at least, the only invariant targets of the speech production process are multidimensional regions in auditory perceptual space. These auditory perceptual target regions are hypothesized to arise during development as an emergent property of neural map formation in the auditory system. Furthermore, speech movements are planned as trajectories in auditory perceptual space. These trajectories are then mapped into articulator movements through a neural mapping that allows motor equivalent variability in constriction locations and degrees when needed, but maintains approximate constriction invariance for a given sound in most instances. These hypotheses are illustrated and substantiated using computer simulations of the DIVA model of speech acquisition and production. Finally, we pose several difficult challenges to proponents of constriction theories based on this theoretical treatment.

The American English phoneme /r/ has long been associated with large amounts of articulatory variability during production. This paper investigates the hypothesis that the articulatory variations used by a speaker to produce /r/ in different contexts exhibit systematic tradeoffs, or articulatory trading relations, that act to maintain a relatively stable acoustic signal despite the large variations in vocal tract shape. Acoustic and articulatory recordings were collected from seven speakers producing /r/ in five phonetic contexts. For every speaker, the different articulator configurations used to produce /r/ in the different phonetic contexts showed systematic tradeoffs, as evidenced by significant correlations between the positions of transducers mounted on the tongue. Analysis of acoustic and articulatory variabilities revealed that these tradeoffs act to reduce acoustic variability, thus allowing relatively large contextual variations in vocal tract shape for /r/ without seriously ...

English distinguishes five front vowels phonetically and phonologically, as

This paper proposes an analysis of phonological vowel reduction according to which vowel contrasts are subject to neutralization in unstressed syllables because it is more difficult to keep vowels distinct where vowel duration is shorter. Where the durational difference between stressed and unstressed vowels is large enough, it may not be possible to realize the same number of vowel contrasts in stressed and unstressed syllables while keeping the unstressed vowels adequately distinct, in which case it is preferable to reduce the size of the unstressed vowel inventory. The analysis is formulated as a numerical model, extending Liljencrants and Lindblom’s (1972) model of vowel inventories by incorporating aspects of the prosodic and segmental contexts of vowels, and allowing for different vowel inventories in different contexts. The model contributes to our understanding of vowel reduction, providing an explanation for the observation that vowel reduction primarily neutralizes height contrasts, and demonstrates how Liljencrants and Lindblom’s modeling approach can be developed to analyze contextual restrictions on the distribution of speech sounds. 1.