Different phase-stable relationships of the upper lip and jaw for production of vowels and diphthongs.

Relational invariants have been reported in the timing of articulatory gestures across suprasegmental changes, such as rate and stress. In the current study, the relative timing of the upper lip and jaw was investigated across changes in both suprasegmental and segmental characteristics of speech. The onset of upper lip movement relative to the vowel-to-vowel jaw cycle during intervocalic bilabial production was represented as a phase angle, and analyzed across changes in stress, vowel height, and vowel/diphthong identity. Results indicated that the relative timing of the upper lip and jaw varied systematically with changes in stress and vowel/diphthong identity, while remaining constant across changes in vowel height. It appears that modifications in relative timing may be due to adjustments in the jaw cycle as a result of the compound nature of jaw movement for diphthongs as compared to vowels, with further modifications due to the effect of stress on these compound movements.     

An examination of intra-articulator relative timing

The relative timing of consonant and vowel related movements of the tongue dorsum across variations in stress patterns was examined in two subjects using a computerized pulsed ultrasound system. The patterns observed were similar to those reported by Tuller et al. [J. Exp. Psychol. H.P.P. 8, 460-472 (1982)] for interarticulator timing. Correlations between the duration of a "period," defined as the interval between the onsets of movements associated with adjacent vowels, and the "latency," defined as the interval between the beginning of the period and the point in the period at which movement associated with the intervocalic consonant begins, were positive and reliable. The source of this correlation pattern was examined and found not to be due to a scaling of an invariant phase relation but rather due to a main effect for stress on the vowel-to-vowel articulatory period combined with an artifactual part-whole correlation within each stress level.     

The timing of articulatory gestures: evidence for relational invariants

In this article, we examine the effects of changing speaking rate and syllable stress on the space-time structure of articulatory gestures. Lip and jaw movements of four subjects were monitored during production of selected bisyllabic utterances in which stress and rate were orthogonally varied. Analysis of the relative timing of articulatory movements revealed that the time of onset of gestures specific to consonant articulation was tightly linked to the timing of gestures specific to the flanking vowels. The observed temporal stability was independent of large variations in displacement, duration, and velocity of individual gestures. The kinematic results are in close agreement with our previously reported EMG findings [B. Tuller et al., J. Exp. Psychol. 8, 460-472 (1982)] and together provide evidence for relational invariants in articulation.     

Interarticulator programming in VCV sequences: lip and tongue movements

This study examined the temporal phasing of tongue and lip movements in vowel-consonant-vowel sequences where the consonant is a bilabial stop consonant /p, b/ and the vowels one of /i, a, u/; only asymmetrical vowel contexts were included in the analysis. Four subjects participated. Articulatory movements were recorded using a magnetometer system. The onset of the tongue movement from the first to the second vowel almost always occurred before the oral closure. Most of the tongue movement trajectory from the first to the second vowel took place during the oral closure for the stop. For all subjects, the onset of the tongue movement occurred earlier with respect to the onset of the lip closing movement as the tongue movement trajectory increased. The influence of consonant voicing and vowel context on interarticulator timing and tongue movement kinematics varied across subjects. Overall, the results are compatible with the hypothesis that there is a temporal window before the oral closure for the stop during which the tongue movement can start. A very early onset of the tongue movement relative to the stop closure together with an extensive movement before the closure would most likely produce an extra vowel sound before the closure.     

Lip-jaw and tongue-jaw coordination during rate-controlled syllable repetitions

The present study investigated the relationship between functionally relevant compound gestures and single-articulator component movements of the jaw and the constrictors lower lip and tongue tip during rate-controlled syllable repetitions. In nine healthy speakers, the effects of speaking rate (3 vs 5 Hz), place of articulation, and vowel type during stop consonant-vowel repetitions (/pa/, /pi/, /ta/, /ti/) on the amplitude and peak velocity of differential jaw and constrictor opening-closing movements were measured by means of electromagnetic articulography. Rather than homogeneously scaled compound gestures, the results suggest distinct control mechanisms for the jaw and the constrictors. In particular, jaw amplitude was closely linked to vowel height during bilabial articulation, whereas the lower lip component amplitude turned out to be predominantly rate sensitive. However, the observed variability across subjects and conditions does not support the assumption that single-articulator gestures directly correspond to basic phonological units. The nonhomogeneous effects of speech rate on articulatory subsystem parameters indicate that single structures are differentially rate sensitive. On average, an increase in speech rate resulted in a more or less proportional increase of the steepness of peak velocity/amplitude scaling for jaw movements, whereas the constrictors were less rate sensitive in this respect. Negative covariation across repetitions between jaw and constrictor amplitudes has been considered an indicator of motor equivalence. Although significant in some cases, such a relationship was not consistently observed across subjects. Considering systematic sources of variability such as vowel height, speech rate, and subjects, jaw-constrictor amplitude correlations showed a nonhomogeneous pattern strongly depending on place of articulation.     

On the role of spectral transition for speech perception

This paper examines the relationship between dynamic spectral features and the identification of Japanese syllables modified by initial and/or final truncation. The experiments confirm several main points. "Perceptual critical points," where the percent correct identification of the truncated syllable as a function of the truncation position changes abruptly, are related to maximum spectral transition positions. A speech wave of approximately 10 ms in duration that includes the maximum spectral transition position bears the most important information for consonant and syllable perception. Consonant and vowel identification scores simultaneously change as a function of the truncation position in the short period, including the 10-ms period for final truncation. This suggests that crucial information for both vowel and consonant identification is contained across the same initial part of each syllable. The spectral transition is more crucial than unvoiced and buzz bar periods for consonant (syllable) perception, although the latter features are of some perceptual importance. Also, vowel nuclei are not necessary for either vowel or syllable perception.     

Influence of following context on perception of the voiced-voiceless distinction in syllable-final stop consonants

This paper reports acoustic measurements and results from a series of perceptual experiments on the voiced-voiceless distinction for syllable-final stop consonants in absolute final position and in the context of a following syllable beginning with a different stop consonant. The focus is on temporal cues to the distinction, with vowel duration and silent closure duration as the primary and secondary dimensions, respectively. The main results are that adding a second syllable to a monosyllable increases the number of voiced stop consonant responses, as does shortening of the closure duration in disyllables. Both of these effects are consistent with temporal regularities in speech production: Vowel durations are shorter in the first syllable of disyllables than in monosyllables, and closure durations are shorter for voiced than for voiceless stops in disyllabic utterances of this type. While the perceptual effects thus may derive from two separate sources of tacit phonetic knowledge available to listeners, the data are also consistent with an interpretation in terms of a single effect; one of temporal proximity of following context.     

Dynamic spectral structure specifies vowels for children and adults

When it comes to making decisions regarding vowel quality, adults seem to weight dynamic syllable structure more strongly than static structure, although disagreement exists over the nature of the most relevant kind of dynamic structure: spectral change intrinsic to the vowel or structure arising from movements between consonant and vowel constrictions. Results have been even less clear regarding the signal components children use in making vowel judgments. In this experiment, listeners of four different ages (adults, and 3-, 5-, and 7-year-old children) were asked to label stimuli that sounded either like steady-state vowels or like CVC syllables which sometimes had middle sections masked by coughs. Four vowel contrasts were used, crossed for type (front/back or closed/open) and consonant context (strongly or only slightly constraining of vowel tongue position). All listeners recognized vowel quality with high levels of accuracy in all conditions, but children were disproportionately hampered by strong coarticulatory effects when only steady-state formants were available. Results clarified past studies, showing that dynamic structure is critical to vowel perception for all aged listeners, but particularly for young children, and that it is the dynamic structure arising from vocal-tract movement between consonant and vowel constrictions that is most important.     

Effects of stress and final-consonant voicing on vowel production: articulatory and acoustic analyses

Durations of the vocalic portions of speech are influenced by a large number of linguistic and nonlinguistic factors (e.g., stress and speaking rate). However, each factor affecting vowel duration may influence articulation in a unique manner. The present study examined the effects of stress and final-consonant voicing on the detailed structure of articulatory and acoustic patterns in consonant-vowel-consonant (CVC) utterances. Jaw movement trajectories and F 1 trajectories were examined for a corpus of utterances differing in stress and final-consonant voicing. Jaw lowering and raising gestures were more rapid, longer in duration, and spatially more extensive for stressed versus unstressed utterances. At the acoustic level, stressed utterances showed more rapid initial F 1 transitions and more extreme F 1 steady-state frequencies than unstressed utterances. In contrast to the results obtained in the analysis of stress, decreases in vowel duration due to devoicing did not result in a reduction in the velocity or spatial extent of the articulatory gestures. Similarly, at the acoustic level, the reductions in formant transition slopes and steady-state frequencies demonstrated by the shorter, unstressed utterances did not occur for the shorter, voiceless utterances. The results demonstrate that stress-related and voicing-related changes in vowel duration are accomplished by separate and distinct changes in speech production with observable consequences at both the articulatory and acoustic levels.     

Prosodic strengthening and featural enhancement: evidence from acoustic and articulatory realizations of /a,i/ in English

In this study the effects of accent and prosodic boundaries on the production of English vowels (/a,i/), by concurrently examining acoustic vowel formants and articulatory maxima of the tongue, jaw, and lips obtained with EMA (Electromagnetic Articulography) are investigated. The results demonstrate that prosodic strengthening (due to accent and/or prosodic boundaries) has differential effects depending on the source of prominence (in accented syllables versus at edges of prosodic domains; domain initially versus domain finally). The results are interpreted in terms of how the prosodic strengthening is related to phonetic realization of vowel features. For example, when accented, /i/ was fronter in both acoustic and articulatory vowel spaces (enhancing [-back]), accompanied by an increase in both lip and jaw openings (enhancing sonority). By contrast, at edges of prosodic domains (especially domain-finally), /i/ was not necessarily fronter, but higher (enhancing [+high]), accompanied by an increase only in the lip (not jaw) opening. This suggests that the two aspects of prosodic structure (accent versus boundary) are differentiated by distinct phonetic patterns. Further, it implies that prosodic strengthening, though manifested in fine-grained phonetic details, is not simply a low-level phonetic event but a complex linguistic phenomenon, closely linked to the enhancement of phonological features and positional strength that may license phonological contrasts.     

Simultaneous effects on vowel duration in American English: a covariance structure modeling approach

The powerful techniques of covariance structure modeling (CSM) long have been used to study complex behavioral phenomenon in the social and behavioral sciences. This study employed these same techniques to examine simultaneous effects on vowel duration in American English. Additionally, this study investigated whether a single population model of vowel duration fits observed data better than a dual population model where separate parameters are generated for syllables that carry large information loads and for syllables that specify linguistic relationships. For the single population model, intrinsic duration, phrase final position, lexical stress, post-vocalic consonant voicing, and position in word all were significant predictors of vowel duration. However, the dual population model, in which separate model parameters were generated for (1) monosyllabic content words and lexically stressed syllables and (2) monosyllabic function words and lexically unstressed syllables, fit the data better than the single population model. Intrinsic duration and phrase final position affected duration similarly for both the populations. On the other hand, the effects of post-vocalic consonant voicing and position in word, while significant predictors of vowel duration in content words and stressed syllables, were not significant predictors of vowel duration in function words or unstressed syllables. These results are not unexpected, based on previous research, and suggest that covariance structure analysis can be used as a complementary technique in linguistic and phonetic research.     

Jaw and lip movements of deaf talkers producing utterances with known stress patterns

This investigation determined whether prelingually deaf talkers could correctly produce stressed and unstressed syllables across known changes in stress patterning and phonetic composition. Three deaf and three hearing adults spoke sets of homogeneous syllable strings with stress patterns that they could tap successfully with a finger. Strain gauge transduction of lower lip and jaw movement indicated that both deaf and hearing subjects produced different displacements and durations for the stressed and unstressed syllables, regardless of the stress pattern. Jaw movement did not become more variable with changes in phonetic composition of the syllables. The results show no evidence that motoric abilities (as assessed in lip and jaw movements) limit deaf talkers in producing desired stress patterns.     

Can intrinsic vowel Fo be explained by source/tract coupling?

There is extensive evidence that in the same phonetic environment the voice fundamental frequency (Fo) of vowels varies directly with vowel "height." This Fo difference between vowels could be caused by acoustic interaction between the first vowel formant and the vibrating vocal folds. Since higher vowels have lower first formants than low vowels the acoustic interaction should be greatest for high vowels whose first formant frequencies are closer in frequency to Fo. Ten speakers were used to see if acoustic interaction could cause the Fo differences. The consonant [m] was recorded in the utterances [umu] and [ama]. Although the formant structure of [m] in [umu] and [ama] should not differ significantly, the Fo of each [m] allophone was significantly different. However, the Fo of each [m] allophone did not differ significantly from the Fo of the following vowel. These results did not support acoustic interaction. However, it is quite reasonable to conclude that the Fo variation of [m] was caused by coarticulatory anticipation of the tongue and jaw for the following vowel. Another experiment is offered in order to help explain the physical causes of intrinsic vowel Fo. In this experiment Fo lowering was found at the beginning of vowels following Arabic pharyngeal approximants. This finding indicates that the Fo of pharyngeal constricting vowels, e.g., [ae] and [a], might be lowered as a result of similar articulary movements, viz. tongue compression and active pharyngeal constriction.     

The effect of emphatic stress on consonant vowel coarticulation

This study assessed the acoustic coarticulatory effects of phrasal accent on [V1.CV2] sequences, when separately applied to V1 or V2, surrounding the voiced stops [b], [d], and [g]. Three adult speakers each produced 360 tokens (six V1 contexts x ten V2 contexts x three stops x two emphasis conditions). Realizing that anticipatory coarticulation of V2 onto the intervocalic C can be influenced by prosodic effects, as well as by vowel context effects, a modified locus equation regression metric was used to isolate the effect of phrasal accent on consonantal F2 onsets, independently of prosodically induced vowel expansion effects. The analyses revealed two main emphasis-dependent effects: systematic differences in F2 onset values and the expected expansion of vowel space. By accounting for the confounding variable of stress-induced vowel space expansion, a small but consistent coarticulatory effect of emphatic stress on the consonant was uncovered in lingually produced stops, but absent in labial stops. Formant calculations based on tube models indicated similarly increased F2 onsets when stressed /d/ and /g/ were simulated with deeper occlusions resulting from more forceful closure movements during phrasal accented speech.     

The articulatory kinematics of final lengthening

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.     

Anticipatory coarticulation: some implications from a study of lip rounding.

The anticipation of articulatory features, in particular lip rounding in anticipation of a rounded vowel, has been reported to occur as many as four segments before the segment for which the feature is specified. In the data presented here, we find that the moter commands for the rounding gesture for /u/ begin a fixed time before the onset of the vowel. This timing is unaffected by the number of consonant segments in the preceding string. Thus, the initiation of lip rounding appears to be linked to other features of the vowel articulation.     

A comparison of intergestural patterns in deaf and hearing adult speakers: implications from an acoustic analysis of disyllables.

Coarticulation studies in speech of deaf individuals have so far focused on intrasyllabic patterning of various consonant-vowel sequences. In this study, both inter- and intrasyllabic patterning were examined in disyllables /symbol see text #CVC/ and the effects of phonetic context, speaking rate, and segment type were explored. Systematic observation of F2 and durational measurements in disyllables minimally contrasting in vocalic ([i], [u,][a]) and in consonant ([b], [d]) context, respectively, was made at selected locations in the disyllable, in order to relate inferences about articulatory adjustments with their temporal coordinates. Results indicated that intervocalic coarticulation across hearing and deaf speakers varied as a function of the phonetic composition of disyllables (b_b or d_d). The deaf speakers showed reduced intervocalic coarticulation for bilabial but not for alveolar disyllables compared to the hearing speakers. Furthermore, they showed less marked consonant influences on the schwa and stressed vowel of disyllables compared to the hearing controls. Rate effects were minimal and did not alter the coarticulatory patterns observed across hearing status. The above findings modify the conclusions drawn from previous studies and suggest that the speech of deaf and hearing speakers is guided by different gestural organization.     

A study of jaw coarticulatory resistance and aggressiveness for Catalan consonants and vowels

The goal of this study is to investigate coarticulatory resistance and aggressiveness for the jaw in Catalan consonants and vowels and, more specifically, for the alveolopalatal nasal //[symbol see text]/ and for dark /l/ for which there is little or no data on jaw position and coarticulation. Jaw movement data for symmetrical vowel-consonant-vowel sequences with the consonants /p, n, l, s, ∫, [ symbol see text], k/ and the vowels /i, a, u/ were recorded by three Catalan speakers with a midsagittal magnetometer. Data reveal that jaw height is greater for /s, ∫/ than for /p, [see text]/, which is greater than for /n, l, k/ during the consonant, and for /i, u/ than for /a/ during the vowel. Differences in coarticulatory variability among consonants and vowels are inversely related to differences in jaw height, i.e., fricatives and high vowels are most resistant, and /n, l, k/ and the low vowel are least resistant. Moreover, coarticulation resistant phonetic segments exert more prominent effects and, thus, are more aggressive than segments specified for a lower degree of coarticulatory resistance. Data are discussed in the light of the degree of articulatory constraint model of coarticulation.     

Consonant confusions in white noise

The classic [MN55] confusion matrix experiment (16 consonants, white noise masker) was repeated by using computerized procedures, similar to those of Phatak and Allen (2007). ["Consonant and vowel confusions in speech-weighted noise," J. Acoust. Soc. Am. 121, 2312-2316]. The consonant scores in white noise can be categorized in three sets: low-error set [/m/, /n/], average-error set [/p/, /t/, /k/, /s/, /[please see text]/, /d/, /g/, /z/, /Z/], and high-error set /f/theta/b/, /v/, /E/,/theta/]. The consonant confusions match those from MN55, except for the highly asymmetric voicing confusions of fricatives, biased in favor of voiced consonants. Masking noise cannot only reduce the recognition of a consonant, but also perceptually morph it into another consonant. There is a significant and systematic variability in the scores and confusion patterns of different utterances of the same consonant, which can be characterized as (a) confusion heterogeneity, where the competitors in the confusion groups of a consonant vary, and (b) threshold variability, where confusion threshold [i.e., signal-to-noise ratio (SNR) and score at which the confusion group is formed] varies. The average consonant error and errors for most of the individual consonants and consonant sets can be approximated as exponential functions of the articulation index (AI). An AI that is based on the peak-to-rms ratios of speech can explain the SNR differences across experiments.