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Articulatory and acoustic variability in the production of five American English vowels was examined. The data were movement records for selected fleshpoints on the midsagittal tongue surface, recorded using the x-ray microbeam. An algorithm for nonlinearly transforming fleshpoint positions to a new Cartesian space in which the x and y axes represent, respectively, the distance of the fleshpoint along the opposing vocal tract wall and the distance perpendicular to the tract wall, is described. The transformation facilitates a test of Quantal Theory in which variability in the two dimensions is compared over many productions of a given vowel type. The data provide some support for the theory. For fleshpoints near ''quantal'' constriction sites, the primary variability was in the x dimension (constriction location). The y-dimension values were more tightly constrained, and the formant frequencies were more significantly correlated with the y values than with the x values. The greater variability in constriction location than in degree was not an artifact of the greater distances traversed in the x dimension between the vowel and constrictions in neighboring consonants, since the pattern was preserved when pellet values were translated to take into account a ''context-free'' vowel target (the average values in the context of preceding and following labial consonants). Moreover, the observed correlations between formant values and pellet positions in the two dimensions for [i] and [u] were duplicated in an articulatory-to-acoustic modeling test using values for constriction length and cross-sectional area estimated from the data. The model showed smaller second formant variability in the x dimension than in the y dimension for equal-sized excursions near the constriction sites for these close vowels, in keeping with the interpretation that speakers exercise less precise control in just the dimensions and regions where quantal stability is available. However, the articulatory pattern was seen not just in vowels which clearly have consonantlike constrictions (the quantal vowels [i], [u], and [@sa ]), but also in nonquantal vowels such as [æ]. [ABSTRACT FROM AUTHOR]

In order to understand better the phonetic control of final lengthening, the articulation of phrase-final syllables was compared with that of two other contexts known to increase syllable duration: accent and slow tempo. The kinematics of jaw movements in [pap] sequences and of lower lip movements in [pE] sequences for four subjects were interpreted in terms of a task-dynamic model. There was evidence of two different control strategies: decreasing intragestural stiffness to slow down some part of the syllable, and changing intergestural phasing to decrease overlap of the vowel gesture by the consonant. The first was used in slowing down tempo, whereas the second was used to increase the duration of accented syllables over unaccented syllables. Both strategies were implicated in phrase-final lengthening. In accented syllables, final closing gestures generally were longer and slower, but not more displaced. The two slowest subjects, however, used the other strategy in their slow-tempo final syllables. Final lengthening in reduced syllables was more difficult to interpret. The relationship between peak velocity and displacement suggested that a lesser stiffness is obscured by an increased gestural amplitude. Thus, by comparison to lengthening for accent, final lengthening is like a localized change in speaking tempo, although it cannot be equated directly with the specification of stiffness. [ABSTRACT FROM AUTHOR]

Earlier experiments have shown that Japanese and English differ in the extent to which they use duration and vowel amplitude patterns as acoustic correlates of lexical accent [M. E. Beckman, J. Acoust. Soc. Am. Suppl. 1 71, S23 (1982); J. Acoust. Soc. Am. Suppl. 1 75, S41 (1984)]. A new experiment examines the relative salience of various acoustic correlates as perceptual cues in the two languages. Minimally contrasting test utterance pairs from the earlier production experiments were used to synthesize test stimuli with all possible combinations of acoustic patterns (e.g., the F0 and amplitude patterns of contráct combined with the duration and spectral quality patterns of cóntract). Japanese, Americans with speaking knowledge of Japanese, and monolingual Americans judged the accent patterns of these test stimuli. Results showed differences correlated both with the source language of the stimulus, and with the language background of the subject. For all three groups, F0 was the dominant cue to the accent patterns of the Japanese stimuli, scoring significantly higher than it did in the judgments of the English stress patterns by the same group. In judging the English stimuli, the monolingual American subjects relied on acoustic cues other than F0 to a greater extent than did the bilingual Americans, although both American groups used them to a greater extent than did the Japanese subjects, most of whose scores for amplitude, duration, and spectral quality patterns were at chance. [ABSTRACT FROM AUTHOR]

Intonation pattern and syllable duration are thought to be the most salient perceptual cues to phrase stress. However, intonation is an inherently ambiguous cue, since not all English pitch accents involve higher pitch on the accented syllable, and because there are stress contrasts at a lower level, where stress cannot be equated with accentuation. Duration, too, is ambiguous, since it can cue other prosodic contrasts, such as phrasal position. This study examines finer-grained timing cues to stress. A strain-gauge system was used to examine jaw opening and closing movements in /popen ayep/ sequences in intonationally accented full-voweled syllables, unaccented full-voweled syllables, and completely stressless (reduced-vowel) syllables produced by four speakers. Measured values for movement duration, displacement, and velocity were consistently larger in accented than in unaccented full-voweled syllables. However, these differences were nowhere near as large as the differences between full- and reduced-vowel syllables. Reduced syllables also had steeper velocity-displacement relationships, suggesting a durational difference at the level of gestural dynamics as well. However, no such consistent difference was observed between accented and unaccented full-voweled syllables. These results support the notion that stress contrasts are not uniformly interpreted in the phonetics at different levels. [ABSTRACT FROM AUTHOR]

Various linguistic roles have been hypothesized for the jaw. In Browman and Goldstein's Articulatory Phonology, it is identified as the common articulator among gestures involving the lower lip, tongue tip, and tongue body, and Goldstein has suggested that this may underly the differentiation in Arabic phonology between oral consonants (labials, dentals, velars) and gutturals (uvulars, pharyngeals, glottals). Keating (1983) proposed that consonants are specified for relatively fixed jaw heights (sibilants higher than stops higher than glides), providing the phonetic basis for sonority sequencing constraints. Macchi (1985) proposed that jaw height during consonants reflects both a passive coarticulation with neighboring vowels, and an active suprasegmental specification (lower in stressed syllables). This paper re-examines these hypotheses using a corpus contrasting different places of articulation. The hypotheses are supported more or less well, depending on place. For example, Macchi's hypothesis was borne out for labials, but the jaw was quite low during velar stops in unstressed syllables, usually lower than in the preceding vowel. These results suggest that no linguistic role can be stated straightforwardly for all consonants. Rather, the jaw's contribution varies in proportion to the distance of the oral articulator from the condyle. [Work supported by the NSF.] [ABSTRACT FROM AUTHOR]

This paper compares the articulatory correlates of lengthening at phrase boundaries to those of slowing down from normal to slow tempo. The velocity, displacement, and duration of opening and closing mandibular gestures of syllables in intonation-phrase-final and nonfinal position were examined for four speakers. The longer durations of phrase-final syllables are due primarily to slower closing gestures, without any accompanying differences in articulator displacement. Similarly, changing from normal to slow tempo is effected by a decrease in peak velocity for both the opening and closing gestures, without any accompanying differences in articulator displacement. Thus final lengthening can be described as a local slowing down before the phrase boundary. Interestingly, two subjects did not differentiate between the peak velocity of final and nonfinal closing gestures at the slow rate, probably because they had reached a lower limit on peak velocity. However, these subjects did maintain a difference in vowel period duration between nonfinal and final syllables at the slow tempo. This result suggests that final lengthening has a directly temporal target at a more abstract level of specification than the articulatory dynamics. [Work supported by the National Science Foundation under grants IRI-8617873 and IRI-8617852.] [ABSTRACT FROM AUTHOR]

Linguistic characterizations of English stress patterns typically claim that when one stressed syllable is followed immediately by another and the rhythmic clash is not corrected by retracting the first stress to an earlier position, then the first vowel will be protracted, increasing the phonetic separation between the adjacent beats and thereby regularizing the rhythm. Acoustic studies, however, consistently show that the mean duration for the first vowel in such a stress clash is not substantially longer than that of its counterpart in an alternating stress pattern. Examination of articulatory correlates suggests an explanation for this discrepancy: Syllables in a stress clash may undergo a rhythmic reorganization of segmental gestures that can distance the first syllable's prosodic peak from the following stress without lengthening the vowel's measured duration. Displacements, durations, and peak velocities of jaw opening and closing gestures were measured for four speakers' productions of stress clash sequences Pop posed and alternating stress sequences Pop opposed. In general, the jaw opening gesture was relatively shorter and the closing gesture relatively longer in the stress clash context. If the degree of jaw opening is taken as an approximation to the sonority contour within the syllable, this result means that the prosodic peak occurred relatively earlier within the initial [pap] in Pop posed. [Work supported by the National Science Foundation under grants IRI-8617852 to Mary Beckman and IRI-8617873 to Jan Edwards.] [ABSTRACT FROM AUTHOR]

A syllable at the end of a phrase is considerably longer than it would be phrase-internally. Similarly, a stressed monosyllable is generally longer than any identical syllable separated from the word's edge by one or more unstressed syllables. Two sets of experiments have been designed to determine the phonological domain of these effects. The first compared target syllables at various distances from the ends of words ([p[variant_greek_epsilon]] in pep, pepper, peppermint; [pa] in pop opposed, poppa posed) in sentences where they either did or did not precede an obligatory intonational phase break. These experiments showed that (1) there is a smaller word-final effect distinct from the substantial phrase-final lengthening at intonational boundaries, and (2) the word-final effect must also be a boundary effect rather than a result of stress timing, since it occurred even in the pop opposed-poppa posed utterances, where the target syllable was always followed by exactly one unstressed syllable. The second set of experiments tests whether word-final lengthening is affected by pitch-accent and stress placement, or whether it defines a phrasal unit independent of metrics. [ABSTRACT FROM AUTHOR]

Studies of Japanese intonation have unanimously shown that fundamental frequency (F0) tends to fall during the course of an utterance. Previous synthesis systems for Japanese have all modeled this F0 trend using the single mechanism of a declining overall tonal reference line that is reset at the beginning of each utterance or major phrase. Recent research by Poser, however, suggests that a more accurate model must account for most of the F0 decline by means of 'downstep,' a sudden step-like reduction of the reference line that is triggered by the accentual pattern of the preceding minor phrase [W. J. Poser, 'On the mechanism of F0 downdrift in Japanese,' J. Acoust Soc. Am. Suppl. 1 74, S89 (1983)]. This paper describes a synthesis program for Japanese intonation that incorporates downstep. The program is being used to investigate the phonetic correlates of intonational phrasing and the interactions between syntactic phrasing and intonation. A demonstration tape will be played to illustrate the synthesis program. [ABSTRACT FROM AUTHOR]

It has long been known that accent (i.e., lexical stress) is a major factor contributing to variations in both vowel duration and vowel amplitude in English. An earlier experiment [Beckman, J. Acoust. Soc. Am. Suppl. 1 71, S1 (1952)] showed that, by contrast to English, Japanese accentual patterns have only a minimal effect on duration patterns. The present experiment compared accentual effects on amplitude in the two languages. It measured vowel amplitudes in a smaller subset of the minimally contrasting Japanese word pairs used earlier, as well as in a set of comparable English pairs. Three measures of vowel amplitude were obtained; namely, peak amplitude, average amplitude, and total amplitude. All three measures performed substantially worse as criteria for accent in Japanese than in English. [ABSTRACT FROM AUTHOR]

SRS, Hertz's language-independent synthesis rule development system, has been used recently to write a set of phoneme-based rules for Japanese. This paper will describe the Japanese prosody rules, which operate on phonological phrases of various sizes to generate natural-sounding prosodic patterns. The phrases are demarcated in the romanized input string by an easy-to-learn annotation scheme. The annotations are translated into boundary symbols and associated boundary features. These features, together with accent marks, are used to generate a segment-by-segment specification by prosody features, such as [low] (low-pitched) and [ace] (accented). Synthesizer parameter rules then refer either to the boundaries' features or to the intervening segments' features to produce various aspects of an utterances' prosodic pattern, such as phrase-final lengthening or the post-accentual pitch fall. Thus, although SRS in its present implementation allows only one level of explicit user-defined synthesis unit, it is relatively easy to set up implicit units of the larger sizes needed to write straightforward prosody rules. [ABSTRACT FROM AUTHOR]

A study reported at an earlier meeting of this Society examined fine-grained timing cues to three levels of stress by comparing jaw kinematics in intonationally accented syllables (with full vowels), unaccented syllables (with full vowels), and completely stressless (reduced-vowel) syllables. For all four speakers in the study, measured values for movement duration, displacement, and peak velocity were consistently largest in the accented syllables and smallest in the reduced-vowel syllables. This study examines the relationships among these kinematic measures using two different models of the underlying gestural dynamics. The first generated shorter (less stressed) syllables by decreasing the latency of the closing gesture relative to the opening gesture without changing the targeted gestural speed or displacement. The second generated shorter syllables by changing the targeted gestural speed, but decreasing targeted displacement more, so as not to increase the predicted velocities. The first model generated predicted durations, which were closer to the observed distribution of durations among the three stress types, whereas the second generated predicted displacements that were closer to the observed distribution of displacements. Neither generated the observed distribution of velocities, suggesting that a hybrid model is necessary. [ABSTRACT FROM AUTHOR]

Since the jaw's vertical displacement is largely due to rotation about the condyle, its contribution to a consonant's constriction should depend on distance from the condyle. An earlier study of one speaker's productions of English stops showed higher jaw in labials than in velars, as predicted, but highest jaw in coronals. This study investigates more consonant types produced by three speakers each of Korean, French, and Arabic. In general, the hypothesized dependency was supported. Jaw height was greater in labials than in velars, and greater in velars than in uvulars, but contributed nothing to pharyngeals and laryngeals. However, the problematic results concerning coronals were confirmed; the jaw was highest in coronals, particularly [s] and [∫ ]. Moreover, in Korean the jaw was higher in velars coarticulated with a neighboring central vowel [barred eye] than coarticulated with the fronter [i]. The greater contribution to coronal fricatives may be because the lower incisors must be positioned to impinge on the air stream, whereas the greater height for dorsal stops next to [barred eye] may be because the opposing surface (the hard palate) is furthest away from the tongue in that place. [ABSTRACT FROM AUTHOR]

Quantal theory claims that sounds which are common in phoneme inventories, such as [i] and [a], are articulated in vocal tract regions where acoustic patterns are relatively insensitive to variation in constriction location. Perkell and Nelson [J. Acoust. Soc. Am. 77, 1889-1895 (1985)] tested this claim using a principal components analysis of x-ray microbeam data. As predicted, tongue pellets showed most positional variation in an axis parallel to the hard palate in [i] and to the pharynx wall in [a]. An earlier replicative study using [i], [a], and three other vowels [Ahalt et al., J. Acoust. Soc. Am. 89, 1871 (1991)] showed that pellet data are more easily interpreted in terms of relative variation in constriction location and degree if they are transformed nonlinearly into a coordinate space where x and y values express location along and distance from the opposing wall of the vocal tract. The present study examined the relationship between formant values and pellet positions in this transformed space, and found some support for quantal theory. In particular, all good correlations involved positional variation in the y dimension for pellets near the constriction. [Work supported by the NSF.] [ABSTRACT FROM AUTHOR]

Two prosodic categories are particularly interesting for examining the relationship between phonetic units and articulatory timing because they provide a clear contrast in prosodic function: The durational correlates of 'sentence stress' mark constituent peaks (nuclear-accented syllables), whereas phrase-final lengthening marks constituent edges. When kinematic patterns are contrasted in nuclear-accented versus unaccented and phrase-final versus nonfinal syllables, it seems that final lengthening is a local decrease in stiffness, whereas lengthening for accent is a change in the phasing of the final (consonant) gesture relative to the opening (vowel) gesture. When interaction with overall tempo is examined, however, it is clear that the prosodic function cannot be equated directly with the dynamic parameters, since at slow tempo, phrase-final lengthening affects phasing rather than stiffness. Thus prosodic structure is not the immediate goal of the dynamic representation. Rather, there must be intermediate representations of the phonetic tasks in terms of a local tempo change (for final lengthening) and an increase in the duration of the 'sonority peak' of the syllable (for sentence stress). [Work supported by the NSF.] [ABSTRACT FROM AUTHOR]

Tongue constriction features can be estimated from sagittal x-ray pictures of the tongue surface and vocal tract wall. However, such records cannot be obtained in quantity, making them unsuitable for testing models such as Stevens's quantal theory. The x-ray microbeam allows larger data sets, but records flesh points rather than surfaces. This paper presents an algorithm for relating the two representations. The vocal tract wall is estimated from whole-head scans and a palate trace. Pellet positions are then 'warped' into a Cartesian space where location along the tract and distance from it are the x and y values. The algorithm has been applied in a replication of Perkell and Nelson's test of quantal theory using principal component analysis. Quantal theory predicts that the pellet closest to the constriction site will show least variability, and that the most precision will be in the dimension perpendicular to the vocal tract wall for 'quantal' vowels such as /i/. In the warped space, then, the principal component of variation for the relevant pellet for these vowels should be parallel to the x axis. This prediction is borne out. [Work supported by the NSF.] [ABSTRACT FROM AUTHOR]

Two recent kinematic studies of syllables with bilabial consonants suggest different dynamic accounts of the durational increase associated with stress: Kelso et al. [J. Acoust. Soc. Am. 77, 266-280 (1985)] interpret regression curves for peak velocity against displacement as evidence that lower-lip gestures in stressed syllables are less stiff, whereas Nittrouer et al. [J. Acoust. Soc. Am. 85, 1653-1661 (1988)] show that the upper-lip closing gesture begins at a later phase relative to the jaw opening gesture. Preliminary results from a kinematic study of accented syllables suggest a resolution of the discrepancy. Jaw opening and closing gestures for pop and poppa embedded in sentences that varied the placement of the nuclear pitch accent (sentence stress) were looked at. When accented, gestures were substantially longer, but the velocity-displacement regression curve showed no decrease in slope, contra Kelso et al. Also, a comparison of observed syllable durations to those predicted by the velocity-displacement ratios showed that this stiffness index alone cannot account for the greater length. Rather, an accented syllable is longer probably because the closing gesture is later, in accordance with Nittrouer et al. The seemingly contradictory pattern in Kelso et al. may be an artifact of including reduced syllables with unaccented full syllables in a single 'unstressed' category. [Work supported by the NSF.] [ABSTRACT FROM AUTHOR]