James Lubker

Formant frequencies of some fixed‐mandible vowels and a model of speech motor programming by predictive simulation

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.

Production of bite‐block vowels: Acoustic equivalence by selective compensation

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 of vocal tract expansion. 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 information, specifically, by information rel...

Anticipatory labial coarticulation: Experimental, biological, and linguistic variables

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.

Temporal Aspects of Speech Production: Anticipatory Labial Coarticulation

This research attempts to define the temporal extent of anticipatory labial coarticulation and the effect on rounding onset of a stressed nonround vowel temporally prior to the rounded vowel. The results suggest that the onset on the labial rounding gesture is controlled in relation to the temporal extent of the nonlabial duration preceding the rounded vowel and that the onset of activity for the rounded vowel is somehow related to the stress of the preceding nonround vowel. These results argue against the classic articulatory syllable model as well as against a concept of the onset of rounding being temporally locked to the rounded vowel. They can be argued to support a look-ahead or scanning model.

The Reorganization Times of Bite-Block Vowels

This investigation attempts to determine, via classical reaction-time techniques, whether speakers require longer times to initiate the production of so-called ‘bite-block’ vowels than they do for normal vowels. The results suggest that speakers do spend measurable amounts of time in neurophysiological reorganization for such vowels. These results are discussed in terms of some current models for speech motor control.

Representation and Context Sensitivity

The paper does not represent an attempt to summarize the current status of reserch in the area of co-articulation. Several good summaries are already avilbale in the literature. Rather, after first establishing that the paper will be concerned solely with that aspect of context sensitivity known as co-articulation, the following main points are taken up: 1. Brief definition of terms used in describing the direction of co-articulation effects. 2. A discussion of the perceptual effects of co-articulation. 3. Some comments on synchronous or interarticulator programming. 4. A consideraion of some of the current issues in co-articulation research and how they relat to some models of speech production theory.

Acoustic-Perceptual Methods for Evaluation of Defective Speech

Publisher Summary Speech is a complex that involves the production and the perception of an acoustic signal. Speech complex involves the following areas of specialization: linguistics, phonology, physiological/ neurological phonetics, acoustics, acoustic phonetics, psychophysics, psychoacoustics, physiological acoustics, and the whole area of perception. A number of human beings are not able to produce an acoustic speech wave, which is perceived by listeners as being normal, if it is understood at all. Another large group of people are unable to perceive or understand a normal acoustic speech wave. These speech- and hearing-disabled individuals provide a dramatic illustration of the elemental importance contained in Jakobsons deceptively simple statement. The clinician must provide diagnosis, prognosis, therapy planning, and evaluation of therapy. These aspects of a clinicians work are dependent upon the understanding of the elements and the relationships in the normal speech communication chain. Diagnosis and prognosis are easily accomplished and expressed in relation to normal production, acoustic, and perception mechanisms. Evaluation of therapy can be viewed as an expression of the patients own self-progress.

Vowel fundamental frequency and tongue height

This research was designed to substantiate the results of Ohala [J. Acoust. Soc. Am. 60, S44(A) (1976)] which supported the “tongue‐pull” hypothesis of intrinsic vowel pitch. Our goal was explanation of the observation that vowels with high tongue position have higher F0 than do vowels with low tongue position. It has been suggested that the anatomical interactions between tongue larynx put an added stress on that structure when the tongue is in an elevated position, thus raising F0 for the vowel. We replicated Ohalas use of bite blocks to force the speaker to produce articulatory “supershapes.” If the tongue‐pull hypothesis is correct. a given vowel would have higher F0 with the jaw blocked in an unnaturally open position than with the jaw free. This was the case with Ohalas results, However, in our preliminary work with three subjects we have not been able to substantiate those results. One of our subjects showed no consistent bite‐block effect on F0, while both of the remaining subjects used a lower ...

Identification of place of articulation in nasal phonemes using a time‐frequency approach

Acoustic cues to place of articulation are present in the highly nonstationary region between nasal consonants and vowels. A need for a speech processing tool capable of accurately representing these transient events led to consideration of the Wignet‐Ville distribution (WVD). Previous use in speech analysis was limited due to the presence of multiple interference terms (crossterms), which hindered its direct interpretation. These crossterms can be attenuated by time‐frequency smoothing (SWVD). Time and frequency resolution may be chosen independently, thus avoiding the trade‐off existing in wide‐ and narrow‐band spectrograms. Despite its apparent complexity, the SWVD can be computed about four times faster than a spectrogram. SWVD analysis of nasal‐vowel transitions accurately shows fine spectrotemporal details in the murmur release, initial slope of the formant transitions, and abrupt energy changes. Identification of place of articulation experiments performed on labial and alveolar nasal consonants in...

Anticipatory labial coarficulation: Extent and influencing variables

This research is designed to investigate the temporal extent of anticipatory (right‐to‐left) co articulation as well as the variables which may influence it. Previous research in this and in other laboratories has suggested that anticipatory coarticulation in lip rounding extends for as much as six consonants or 600 ms prior to a rounded vowel. Some recent work, however, has suggested a more limited extent of such coarticulation. The present work is an attempt to resolve this issue and thus shed some light on cognitive representation and input units for the motor control processes of speech generation. Additionally a number of variables have been proposed to influence the precise location of the anticipatory boundary of labial coarticulation; for example front versus back tongue position for the rounded vowel, stress of the rounded vowel preceding the consonant string. In the present experiment these and other variables are controlled and their effect on the onset of coarticulation is described.