Formant frequency data are reported for Swedish vowels produced both with fixed and unconstrained mandible. Measurements were made at the first glottal pulse to confine interpretation of the results to nonauditory feedback mechanisms. Results indicated that in spite of physiologically unnatural jaw openings, subjects were able to produce F patterns within the ranges of variation of the normal vowels. Results are explained by hypothesizing that the “instantaneous” learning of highly unfamiliar tasks, such as compensatory articulation of fixed-mandible vowels, is possible because normal speech motor programming is indeed “compensatory” rather than due to either speakers drawing upon past similar experience or invoking special motor mechanisms distinct from those of natural speech. That is, it operates in a context-sensitive mode to achieve listener-oriented goals. Since “contexts” constitutes an essentially infinite class of events the programming must be “creative,” or capable of handling conditions never before experienced. A model of speech production is proposed that achieves increased plasticity of motor control by incorporating an “upstairs” predictive component used to simulate “downstairs” processes of execution.

Acoustic and articulatory data are reported for steady state vowels produced both normally and with a bite block. The formant patterns of the bite-block vowels were found to approximate those of the naturally spoken vowels. Measurements derived from lateral view still x-ray films showed that the bite blocks induce drastic articulatory reorganization. Using a mandibular frame of reference, we found that speakers compensated for a large bite block by using supershapes of the tongue and the lips (for [u] and [o]). Comparing the two productions using a maxillary frame of reference, we noted that compensation was maximum at the points of maximum constriction and incomplete or partial at points where the vocal-tract area was large. A computer simulation of our speakers' compensatory strategy revealed that they behaved optimally according to acoustic theory. These findings suggest that a vowel target is coded neurophysiologically in terms of acoustically significant area-function, specifically, by information related to cavity configuration at points of maximum constriction.

No abstract

The research reported here represents an attempt to resolve the differences between two views of anticipatory labial coarticulation. One of these views contends that a speaker begins labial movement toward a rounded vowel in direct relation to the amount of time available, while the other view posits an onset of movement that is temporally locked to the rounded vowel. Electromyographic signals were sampled from four muscles associated with labial movement while, simultaneously, movements of the upper lip in the anterior-posterior and vertical dimensions were recorded. Four native speakers of American English and five native speakers of Swedish served as subjects. Results suggested that (1) there are a number of purely biological and experimental variables which can intrude upon research of this type, and (2) there are also language-specific differences in the production of rounded vowels which suggest that Swedish and American English speakers have learned different motor-programming goals. This second observation is discussed in terms of acoustic/perceptual needs of the speakers of a language.

Cinéfluorographic films of velar movement were made simultaneously with surface electromyographic recordings of velar muscle contraction during the production of selected syllables and sustained vowel and nasal phonemes. The data were analyzed to determine (1) the extent of variation in velar position during the production of various phonemes in relation to alterations in duration and phonetic context; (2) the extent of variation in velar electromyographic activity during the same speech utterances; and (3) the extent to which velar elevation and electromyographic activity covary during the production of sustained vowel and nasal phonemes and during alterations in duration and phonetic context. These data are discussed in relation to the hypothesis, advanced by certain investigators, that the velum acts in an all-or-none (ON-OFF) fashion.