Vowel Context Research Articles

Variation in the articulation of Russian stressed vowels and the mechanics of palatalization in consonants

A 3D/4D ultrasound study of Russian stressed vowels in the context of ‘soft’ (phonetically palatalized or palatal) versus ‘hard’ consonants reveals that vowels in these two contexts differ systematically in terms of the position of the tongue root while the tongue dorsum is less consistently modified depending on the speaker, vowel or consonant context. This paper proposes that the observed vowel allophony, as well as the softness contrast in Russian consonants, and the contrast between front and central high vowels, are all defined in terms of the feature [ATR].

Evidence for active control of tongue lateralization in Australian English /l/

Research on the temporal dynamics of /l/ production has focused primarily on mid-sagittal tongue movements. This study reports how known variations in the timing of mid-sagittal gestures are related to para-sagittal dynamics in /l/ formation in Australian English (AusE), using three-dimensional electromagnetic articulography (3D EMA). The articulatory analyses show (1) consistent with past work, the temporal lag between tongue tip and tongue body gestures identified in the mid-sagittal plane changes across different syllable positions and vowel contexts; (2) the lateral channel is largely formed by tilting the tongue to the left/right side of the oral cavity as opposed to curving the tongue within the coronal plane; and, (3) the timing of lateral channel formation relative to the tongue body gesture is consistent across syllable positions and vowel contexts, even as the temporal lag between tongue tip and tongue body gestures varies. This last result is particularly informative with respect to theoretical hypotheses regarding gestural control for /l/s, as it suggests that lateral channel formation is actively controlled as opposed to resulting as a passive consequence of tongue stretching. These results are interpreted as evidence that the formation of the lateral channel is a primary articulatory goal of /l/ production in AusE.

The Impact of Clear Speech on the Perceptual and Acoustic Properties of Fricative-Vowel Sequences in Speakers With Dysarthria.

Purpose Studies have reported that clear speech has the potential to influence suprasegmental and segmental aspects of speech, in both healthy and dysarthric speakers. While the impact of clear speech has been studied on the articulation of individual segments, few studies have investigated its effects on coarticulation with multisegment sequences such as fricative-vowel. Objectives The goals of this study are to investigate, in healthy and dysarthric speech, the impact of clear speech on (a) the perception of anticipatory vowel coarticulation in fricatives and (b) the acoustic characteristics of this effect. Method Ten speakers with dysarthria secondary to idiopathic Parkinson's disease were recruited as well as 10 age- and sex-matched healthy speakers. A sentence reading task was performed in natural and clear speaking conditions. The sentences contained words with the initial fricatives /s/ and /ʃ/ preceded by /ə/ and followed by the vowels /i/, /y/, /u/, or /a/. For the perceptual measurements, five listeners were recruited and were asked to predict the upcoming word by listening only to the isolated fricative. Acoustic analyses consisted of spectral moment analysis (M1-M4) on averaged time series. Results Perceptual findings report that identification rates were improved with clear speech for the speakers with dysarthria, but only for the fricative-/i/ sequences. Error pattern analysis indicates that this improvement is associated with an increase in the roundness parameter (lip spreading) identification. Acoustic results are unclear for M1 and M3 but suggest that M2 and M4 differentiation between the rounded versus unrounded vowel contexts is increased with clear speech for the speakers with dysarthria. Discussion Taken together, these findings suggest that clear speech may improve lip coordination in dysarthric speakers with Parkinson's disease. However, the impact of clear speech on the acoustic measures of fricative spectral moments is somewhat limited. This suggests that these metrics, when taken individually, do not capture the entire complexity of fricative-vowel coarticulation.

Coarticulation and learnability of transparent vowels in vowel harmony

The representations of transparent vowels in vowel harmony have been of interest to phonologists because of the challenges they pose for constraints on locality and complexity. One proposal is that transparent vowels in back vowel harmony may be intermediate between front and back. The present study uses two artificial language learning experiments to explore the psychological reality of acoustic differences in transparent vowels in back vs. front vowel contexts. Participants were exposed to a back/round vowel harmony language with a neutral vowel that was spliced so that the F2 was lower in back vowel contexts and higher in front vowel contexts (the Natural condition) or the reverse (the Unnatural condition). While only participants in the Natural condition of Experiment 1 were able to learn the behavior of the transparent vowel relative to a No-Training control, there was no difference between the Natural and Unnatural conditions. In Experiment 2, only participants in the Natural condition learned the vowel harmony pattern, though there were no significant differences between the two conditions. No condition successfully learned the behavior of the transparent vowel in Experiment 2. These results suggest that the effects of small differences in the F2 value of transparent back vowels on learnability are minimal.

The Dorsal Differentiation of Velar From Alveolar Stops in Typically Developing Children and Children With Persistent Velar Fronting.

Purpose This study has two key aims: first, to provide developmental articulatory norms for the alveolar-velar distinction in 30 English-speaking typically developing (TD) children; second, to illustrate the utility of the reported measures for classifying and quantifying the speech of children with a history of persistent velar fronting as they develop the contrast longitudinally. Method This study involved secondary data analysis of the UltraSuite corpus comprising ultrasound tongue imaging recordings of speech materials from 30 typical children and longitudinal data from five children with persistent velar fronting undergoing ultrasound visual biofeedback intervention. We present two new measures of coronal dorsal differentiation: KTMax and KT crescent area. These measures distinguish /k/ and /t/ by quantifying the magnitude of this distinction in absolute spatial terms (mm of linear dorsal difference). For the typical children, we report these measures in corner vowel contexts. We then compare these to dorsal productions by the children with speech disorders, before, during, and after intervention. Results Both measures reliably distinguished /k/ and /t/ in TD children. There was an effect of vowel, with larger KTmax and KT crescent area in /a/ and /o/ vowel contexts than in an /i/ context. The children with persistent velar fronting showed KTmax values near zero before intervention, showing a complete merger between /k/ and /t/. During intervention, they showed variable KTmax values. Post intervention, they showed values within the range of typical children. Conclusions This study provides articulatory norms derived from ultrasound tongue imaging for the dorsal differentiation in alveolar and velar stops in TD children. By applying these norms to children with persistent velar fronting as they acquire this contrast, we see that /k/ is acquired in an articulatorily gradient manner.

A Study of the Vowel Context Effect on Initial Stops of Mandarin Produced by Native and Nonnative Speakers

This study, based on corpus materials, investigates the “voice onset time” (VOT) of Mandarin word-initial stops in isolated syllables according to the effect of vowel contexts produced by native and nonnative speakers. Here, 1250 monosyllables of word-initial plosives /p/, /t/, /k/, /p[Formula: see text]/, /t[Formula: see text]/, and /k[Formula: see text]/ were uttered in combination with the vowels /a/, /i/, and /u/ in four tone contexts except /ki/ and /k[Formula: see text]i/ that are phonetically illegal in Mandarin by 20 participants (10 native Chinese speakers and 10 Urdu learners of Chinese). Results show that for native Chinese speakers, the VOTs of aspirated stops followed by the high vowels /i/ and /u/ are significantly longer than those followed by the low vowel /a/, and unaspirated stops followed only by the high back vowel /u/ are significantly longer than those followed by the low vowel /a/. For native Urdu speakers, the mean VOTs of word-initial stops in Mandarin monosyllables have no significant effect for both aspirated and unaspirated ones in combination with different vowels. Understanding the results of this study will be of assistance to second language learning and teaching.

Oral configurations during vowel nasalization in English

Speech nasalization is achieved primarily through the opening and closing of the velopharyngeal port. However, the resultant acoustic features can also be influenced by tongue configuration. Although vowel nasalization is not contrastive in English, two previous studies have found possible differences in the oral articulation of nasal and oral vowel productions, albeit with inconsistent results. In an attempt to further understand the conflicting findings, we evaluated the oral kinematics of nasalized and non-nasalized vowels in a cohort of both male and female American English speakers via electromagnetic articulography. Tongue body and lip positions were captured during vowels produced in nasal and oral contexts (e.g., /mɑm/, /bɑb/). Large contrasts were seen in all participants between tongue position of /æ/ in oral and nasal contexts, in which tongue positions were higher and more forward during /mæm/ than /bæb/. Lip aperture was smaller in a nasal context for /æ/. Lip protrusion was not different between vowels in oral and nasal contexts. Smaller contrasts in tongue and lip position were seen for vowels /ɑ, i, u/; this is consistent with biomechanical accounts of vowel production that suggest that /i, u/ are particularly constrained, whereas /æ/ has fewer biomechanical constraints, allowing for more flexibility for articulatory differences in different contexts. Thus we conclude that speakers of American English do indeed use different oral configurations for vowels that are in nasal and oral contexts, despite vowel nasalization being non-contrastive. This effect was consistent across speakers for only one vowel, perhaps accounting for previously-conflicting results.

Formant Trajectory Patterns of American English /l/ Produced by Adults and Children.

Purpose Most acoustic and articulatory studies on /l/ have focused on either duration, formant frequencies, or tongue shape during the constriction interval. Only a limited set of data exists for the transition characteristics of /l/ to and from surrounding vowels. The aim of this study was to examine second formant (F2) transition characteristics of /l/ produced by young children and adults. This was to better understand articulatory behaviors in the production of /l/ and potential clinical applications of these data to typical and delayed /l/ development. Method Participants included 17 children with typically developing speech between the ages of 2 and 5 years, and 10 female adult speakers of Southern American English. Each subject produced single words containing pre- and postvocalic /l/ in two vowel contexts (/i, ɪ/ and /ɔ, ɑ/). F2 transitions, out of and into /l/ constriction intervals from the adjacent vowels, were analyzed for perceptually acceptable /l/ productions. The F2 transition extent, duration, and rate, as well as F2 loci data, were compared across age groups by vowel context for both pre- and postvocalic /l/. Results F2 transitions of adults' /l/ showed a great similarity across and within speakers. Those of young children showed greater variability, but became increasingly similar to those of adults with age. The F2 loci data seemed consistent with greater coarticulation among children than adults. This conclusion, however, must be regarded as preliminary due to the possible influence of different vocal tract size across ages and variability in the data. Conclusions The results suggest that adult patterns can serve as a reliable reference to which children's /l/ productions can be evaluated. The articulatory configurations associated with the /l/ constriction interval and the vocal tract movements into and out of that interval may provide insight into the underlying difficulties related to misarticulated /l/.

A practical method of estimating the time-varying degree of vowel nasalization from acoustic features.

This paper presents a simple and easy-to-use method of creating a time-varying signal of the degree of nasalization in vowels, generated from acoustic features measured in oral and nasalized vowel contexts. The method is presented for separate models constructed using two sets of acoustic features: (1) an uninformed set of 13 Mel-frequency cepstral coefficients (MFCCs) and (2) a combination of the 13 MFCCs and a phonetically informed set of 20 acoustic features of vowel nasality derived from previous research. Both models are compared against two traditional approaches to estimating vowel nasalization from acoustics: A1-P0 and A1-P1, as well as their formant-compensated counterparts. Data include productions from six speakers of different language backgrounds, producing 11 different qualities within the vowel quadrilateral. The results generated from each of the methods are compared against nasometric measurements, representing an objective "ground truth" of the degree of nasalization. The results suggest that the proposed method is more robust than conventional acoustic approaches, generating signals which correlate strongly with nasometric measures across all vowel qualities and all speakers and accurately approximate the time-varying change in the degree of nasalization. Finally, an experimental example is provided to help researchers implement the method in their own study designs.

Respect the surroundings: Effects of phonetic context variability on infants' learning of minimal pairs.

Fourteen-month-olds' ability to distinguish a just learned word, /buːk/, from its minimally different word, /duːk/, was assessed under two pre-exposure conditions: one where /b, d/-initial forms occurred in a varying vowel context and another where the vowel was fixed but the final consonant varied. Infants in the experiments benefited from the variable vowel but not from the variable final consonant context, suggesting that vowel variability but not all kinds of variability are beneficial. These results are discussed in the context of time-honored observations on the vowel-dependent nature of place of articulation cues for consonants.

Realisation of Voice Onset Time (VOT) and Its Implication on Voicing of English (RP) Stops in Ghanaian English (GhE)

There has been a general perception that the English voiced stops /b, d, g/ before and after a pause or silence are more often confused with the initial voiceless stops /p, t, k/. Thus, in distinguishing the two, listeners most often depend on the onset of voicing of the following segments. Voice onset time, therefore, serves as a significant cue in distinguishing English voiced stops from their voiceless counterparts. Interestingly, voiceless stops in many Ghanaian indigenous languages appear to be weakly aspirated; they are perceived to be made with a very short voice onset time. However, listeners are able to distinguish the voiceless stops from their voiced counterparts. What this study sought to do was to investigate the production of English initial voiceless stops, /p, t, k/ in Ghanaian English. Specifically, it sought to examine the voice onset time of the stops, and whether listeners are able to distinguish English stops made with weak aspiration from the voiced stops before and after a pause. The study used 112 Ghanaian speakers, 76 for a production test; they produced 21 tokens of the stops in a /p/-, /t/- and /k/- initial words, and 36 for a perception test; they listened to words produced with voiced stops in a /b-b/, /d-d/ and /g-g/ environments. The study has revealed that for all the voiceless stops, voicing for the following segments began after the stops were released, and there was no pre-voicing or voice lead. However, for some of the stops, voicing coincided with the release, while for some voicing began after an appreciable amount of time after the release burst. The length of the VOT was found to have been affected by place of articulation and vowel contexts. However, speaker sex seems to have no effect on the length of the VOT. It is clear that Ghanaian speakers of English would have no difficulty distinguishing weakly aspirated stops from voiced stops before and after a pause. Also, understanding words having the initial voiced stops before and after a pause and weakly aspirated stops produced by Ghanaians will not be a problem to listeners.

Vowel Context Effects on Consonant Repetition in Early Words

Purpose Consonant repetitions within words are a well-attested speech error pattern in children's early speech acquisition. We investigated the role of intervening vowel context in understanding speech forms containing consonant repetitions in early words. Intrasyllabic consonant-vowel (CV) sequences within consonant-vowel-consonant (CVC) and consonant-vowel-consonant-vowel (CVCV) forms containing consonant repetitions were analyzed to evaluate whether children's lack of independent movement control for the tongue in word-level sequences might contribute to these observed speech patterns. Method Spontaneous speech data produced by 10 typically developing children learning American English were analyzed longitudinally from the onset of word use to 36 months. Overall patterns and word shape effects for nine CV combinations occurring in their CVC and CVCV word shapes that contained repeated nonadjacent consonants and the intervening vowel were analyzed. Results Three CV combinations-coronal-front vowel, labial-central vowel, and dorsal-back vowel-occurred at above-chance levels. Preference for these CV patterns was strong in CVCV but not in CVC word shapes. These CV combinations occurred frequently at all time periods analyzed for CVCV's while decreasing across time for CVC's. Conclusions Analysis of intrasyllabic patterns within word forms containing consonant repetitions revealed that consonant repetitions in many early words occurred at above-chance levels in the context of articulatorily compatible vowels. Results suggest that children's production system capacities are an important contributing principle accounting for vowel context effects within word forms containing consonant repetitions during earliest speech acquisition.

Nasal coda neutralization in Shanghai Mandarin: Articulatory and perceptual evidence

Shanghai Mandarin is reported to neutralize /n/ and /ŋ/ after non-low vowels, a change also reported for other varieties of Chinese. However, the place of articulation of the resulting nasal is unclear. We used production and perception experiments to determine the contexts which condition neutralization and the place of articulation of the resulting nasal. Analysis of ultrasound data using a dimensionality reduction technique revealed that neutralization in production was dependent on the height of the preceding vowel: The highest vowel /i/ conditioned a consistent, non-structure-preserving neutralization to a fronted velar or palatal nasal; the mid vowel /ə/ conditioned an inconsistent, structure-preserving neutralization to [n]; and no neutralization occurred after the low vowel /a/. In contrast, Standard Mandarin controls produced the contrast in all vowel contexts. A follow-up perception experiment confirmed that, consistent with complete neutralization, Shanghai Mandarin listeners failed to distinguish alveolar and velar nasals following /i/. More surprisingly, so did Standard Mandarin listeners, suggesting a near merger of the nasal codas following /i/ in Standard Mandarin. Our results provide support for a role for substantive factors in neutralization-driven sound changes.

Articulatory tongue shape analysis of Mandarin alveolar-retroflex contrast.

As existing descriptions are likely too narrow to reflect a broader range of articulatory variability in Mandarin production, this study is undertaken to explore qualitative and quantitative tongue shape analysis in Mandarin sibilants. Tongue movement data are collected from 18 adult Mandarin speakers producing six sibilants in three vowel contexts. Acoustic information is also analyzed to establish the articulatory-acoustic correspondence. In addition to the common retroflex and bunched shapes, the results discovered a humped shape (e.g., a single, posterior lingual constriction) in most of Mandarin retroflex tokens. This shape is one variant of North American English /r/, but yet identified in Mandarin production. The humped shape adds to the literature and expands existing descriptions of Mandarin retroflex tongue configurations. Despite the shape differences, the general many-to-one articulatory-acoustic mappings also holds true for Mandarin retroflexes. However, while curvature analyses based on Cartesian coordinates significantly differentiated contrastive shapes in retroflex production, these analyses were not equally reliable in separating the alveolar-retroflex distinction, likely due to individual differences. The tongue contour changes in the place contrast were instead quantified by calculations with polar coordinates. The preliminary findings on Mandarin retroflexes are discussed in terms of vocal tract morphology, with possible lip protrusion.

Articulation and identification of voiced stop consonants produced by acoustically driven vocal tract modulations

A recently developed model of speech production [Story & Bunton, JASA, 146(4), 2522–2528] was used to generate VCVs that were examined with regard to both articulation and identification of the consonant. In this model, an utterance is generated by specifying relative acoustic events along a time axis. These events consist of directional changes of the vocal tract resonance frequencies called resonance deflection patterns (RDPs) that, when associated with a temporal event function, are transformed via acoustic sensitivity functions, into time-varying modulations of the vocal tract shape. RDPs specifying /b/, /d/, and /g/ would typically be coded as [−1 −1 −1], [−1 1 1], and [−1 1 −1], respectively, indicating, from left to right, the targeted directional shift of the first, second, and third resonances of the vocal tract. In this study, two types of V1CV2 continua were constructed in three vowel contexts (/i, a, u/) by incrementing in small steps (1) the second resonance deflection from −1 to 1, and (2) the third resonance deflection from 1 to −1. The resulting time-varying vocal tract shapes emulate expected articulation patterns for the stop consonants, and a perceptual experiment indicated that listeners identify the consonants based on the polarity of RDP values.

The Impressionistic Study of English /tʃ/ and /ʃ/ in Initial Position by L2 Thai Learners

Although studies on English sound learning by L2 Thai learners have been widely examined, there have been no studies on the production of the English /tʃ/ and /ʃ/ sounds in the initial position by L2 Thai learners with consideration of vowel contexts, the experience of L2 learners and target sounds. The aim of this study is to examine the production of the English /tʃ/ and /ʃ/ sounds in the initial position while taking the aforementioned factors into account. The data was from 48 L2 Thai learners, and the subjects were divided into two groups of university students: English-majors and non-English-majors. The two target sounds: English /tʃ/ and /ʃ/ together with the Thai /tɕʰ/ sound were tested in 27 words (9 words for each target sound). The subjects produced the target sounds five times, and their production was transcribed by two British transcribers. The results showed that the subjects had high target-like production when producing /ʃ/ but low target-like production when producing /tʃ/. In finding the correlation between the factors and the target-like production, neither the vowel contexts nor the experience could account for the production. The only factor that relates to the production of English /tʃ/ and /ʃ/ was the target sounds, i.e. the number of the productions that was deemed non-target-like was significantly higher when the target sound was /tʃ/ than when it was /ʃ/. This suggests that the target sounds, rather than the L2 experience and the vowel contexts, play a significant role in L2 speech production.

Global organization in Spanish onsets

This paper addresses the relation between syllable structure and inter-segmental temporal coordination. The data examined are Electromagnetic Articulometry recordings from six speakers of Central Peninsular Spanish (henceforth, Spanish), producing words beginning with the clusters /pl, bl, kl, gl, pɾ, kɾ, tɾ/ as well as corresponding unclustered sonorant-initial words in three vowel contexts /a, e, o/. In our results, we find evidence for a global organization of the segments involved in these combinations. This is reflected in a number of ways: shortening of the prevocalic sonorant in the cluster-initial case compared to the unclustered case, reorganization of the relative timing of the internal CV subsequence (in a CCV) in the obstruent-lateral context, early vowel initiation, and a strong compensatory relation between the duration of the obstruent-to-lateral transition and the duration of the lateral. In other words, we find that the global organization presiding over the segments partaking in these tautosyllabic CCVs is pleiotropic, that is, simultaneously expressed over a set of different phonetic parameters rather than via a privileged metric such as c-center stability or any other such given single measure (employed in prior works).

Acquisition and Acoustic Patterns of Southern American English /l/ in Young Children.

Purpose The aim of the current study was to examine /l/ developmental patterns in young learners of Southern American English, especially in relation to the effect of word position and phonetic contexts. Method Eighteen children with typically developing speech, aged between 2 and 5 years, produced monosyllabic single words containing singleton /l/ in different word positions (pre- vs. postvocalic /l/) across different vowel contexts (high front vs. low back) and cluster /l/ in different consonant contexts (/pl, bl/ vs. /kl, gl/). Each production was analyzed for its accuracy and acoustic patterns as measured by the first two formant frequencies and their difference (F1, F2, and F2-F1). Results There was great individual variability in /l/ acquisition patterns, with some 2- and 3-year-olds reaching 100% accuracy for prevocalic /l/, while others were below 70%. Overall, accuracy of prevocalic /l/ was higher than that of postvocalic /l/. Acoustic patterns of pre- and postvocalic /l/ showed greater differences in younger children and less apparent differences in 5-year-olds. There were no statistically significant differences between the acoustic patterns of /l/ coded as perceptually acceptable and those coded as misarticulated. There was also no apparent effect of vowel and consonant contexts on /l/ patterns. Conclusion The accuracy patterns of this study suggest an earlier development of /l/, especially prevocalic /l/, than has been reported in previous studies. The differences in acoustic patterns between pre- and postvocalic /l/, which become less apparent with age, may suggest that children alter the way they articulate /l/ with age. No significant acoustic differences between acceptable and misarticulated /l/, especially postvocalic /l/, suggest a gradient nature of /l/ that is dialect specific. This suggests the need for careful consideration of a child's dialect/language background when studying /l/.

Estimation of Subglottal Pressure From Neck Surface Vibration in Patients With Voice Disorders.

Purpose Given the established linear relationship between neck surface vibration magnitude and mean subglottal pressure (Ps) in vocally healthy speakers, the purpose of this study was to better understand the impact of the presence of a voice disorder on this baseline relationship. Method Data were obtained from participants with voice disorders representing a variety of glottal conditions, including phonotraumatic vocal hyperfunction, nonphonotraumatic vocal hyperfunction, and unilateral vocal fold paralysis. Participants were asked to repeat /p/-vowel syllable strings from loud-to-soft loudness levels in multiple vowel contexts (/pa/, /pi/, /pu/) and pitch levels (comfortable, higher than comfortable, lower than comfortable). Three statistical metrics were computed to analyze the regression line between neck surface accelerometer (ACC) signal magnitude and Ps within and across pitch, vowel, and voice disorder category: coefficient of determination (r 2), slope, and intercept. Three linear mixed-effects models were used to evaluate the impact of voice disorder category, pitch level, and vowel context on the relationship between ACC signal magnitude and Ps. Results The relationship between ACC signal magnitude and Ps was statistically different in patients with voice disorders than in vocally healthy controls; patients exhibited higher levels of Ps given similar values of ACC signal magnitude. Negligible effects were found for pitch condition within each voice disorder category, and negligible-to-small effects were found for vowel context. The mean of patient-specific r 2 values was .63, ranging from .13 to .92. Conclusions The baseline, linear relationship between ACC signal magnitude and Ps is affected by the presence of a voice disorder, with the relationship being participant-specific. Further work is needed to improve ACC-based prediction of Ps, across treatment, and during naturalistic speech production.

Nuer Tonal inventory

The tonal system of Nuer has been a matter of much uncertainty. Here we present empirical evidence in favor of a three toneme system with some typologically rare features. One of them is an intriguing case of allotony based on the phonation of the vowel: the High toneme has a falling allotone over modal vowels. Moreover, the Rising toneme has four allotones: a rising, a mid, a low and a falling allotone. The falling allotone of the Rising toneme also occurs only on modal vowels in specific contexts. We suggest that some of the allotonic variation is motivated by tonal contour simplification. We also point out the role of free variation in some of the allotonic alternations, and the constraints that put limits on the free variation between allotones.