Vowel Context Research Articles

Study of tongue-palate pressure patterns during the hold phase in the production of French denti-alveolar and velar stops

ABSTRACT The hold phase of the stop consonants is crucial for a successful production of the release and the acoustic burst. Concurrently, it is also associated with weak acoustic energy and minimal movement, so that conventional acoustic and kinematic approaches are not relevant to investigate motor control. This paper presents an innovative experimental method to study speech motor control during this phase, based on meticulous measurement of the time variation of the mechanical pressure exerted by the tongue against the palate and also characterizing tongue–palate interaction. The concept is based on using miniature transducers with enhanced response characteristics inserted in different locations of the complete denture of edentulous subjects without perturbing the articulation. The study was done with a French-speaking adult whose maxillary denture was duplicated and mounted with six strain gauge transducers. The experiment was done with denti-alveolar and velar stop consonants with two vowel contexts. The results illustrate the potential of such device to analyse speech motor control when contact constrains tongue movements.

The role of production abilities in the perception of consonant category in infants.

The influence of motor knowledge on speech perception is well established, but the functional role of the motor system is still poorly understood. The present study explores the hypothesis that speech production abilities may help infants discover phonetic categories in the speech stream, in spite of coarticulation effects. To this aim, we examined the influence of babbling abilities on consonant categorization in 6- and 9-month-old infants. Using an intersensory matching procedure, we investigated the infants' capacity to associate auditory information about a consonant in various vowel contexts with visual information about the same consonant, and to map auditory and visual information onto a common phoneme representation. Moreover, a parental questionnaire evaluated the infants' consonantal repertoire. In a first experiment using /b/-/d/ consonants, we found that infants who displayed babbling abilities and produced the /b/ and/or the /d/ consonants in repetitive sequences were able to correctly perform intersensory matching, while non-babblers were not. In a second experiment using the /v/-/z/ pair, which is as visually contrasted as the /b/-/d/ pair but which is usually not produced at the tested ages, no significant matching was observed, for any group of infants, babbling or not. These results demonstrate, for the first time, that the emergence of babbling could play a role in the extraction of vowel-independent representations for consonant place of articulation. They have important implications for speech perception theories, as they highlight the role of sensorimotor interactions in the development of phoneme representations during the first year of life.

/l/ velarisation as a continuum.

In this paper, we present a production study to explore the controversial question about /l/ velarisation. Measurements of first (F1), second (F2) and third (F3) formant frequencies and the slope of F2 were analysed to clarify the /l/ velarisation behaviour in European Portuguese (EP). The acoustic data were collected from ten EP speakers, producing trisyllabic words with paroxytone stress pattern, with the liquid consonant at the middle of the word in onset, complex onset and coda positions. Results suggested that /l/ is produced on a continuum in EP. The consistently low F2 indicates that /l/ is velarised in all syllable positions, but variation especially in F1 and F3 revealed that /l/ could be “more velarised” or “less velarised” dependent on syllable positions and vowel contexts. These findings suggest that it is important to consider different acoustic measures to better understand /l/ velarisation in EP.

Directionality in sound change from asymmetries in acoustic distribution

Following the work of John Ohala, historical sound changes are thought to take place by misperception of the input on the part of the listener. Any account of sound change based on misperception, though, faces a paradox: if X sounds like Y, Y should also sound like X, and yet we often see sound changes that are only attested in one direction. A potential solution is to think of phonetic categories as distributions in acoustic space, and so asymmetries in sound change (X > Y, *Y > X) come from asymmetries in the spread of the distribution of X and Y. If X is a very variable phonetic category with a thick-tailed distribution, a high proportion of its tokens should cross the perceptual boundary and be misperceived as Y; if Y has a narrow distribution, only a very small proportion of its tokens should be perceived as X. We predict that unidirectional sound changes should involve a change from a high-variance to a low-variance category. This experiment tests a case study of asymmetric nasal place assimilation (VnpV > VmpV, *VmpV > VnpV) on a sample of six speakers in three vowel contexts. In the contexts aa and ii, the sequence np before the change had a higher-variance distribution of F2 transition (a cue to nasal place) than the sequence mp after the change. In uu, the sequence after the change had the higher variance. These results give partial support to our hypothesis.

Mice can learn phonetic categories.

Speech is perceived as a series of relatively invariant phonemes despite extreme variability in the acoustic signal. To be perceived as nearly-identical phonemes, speech sounds that vary continuously over a range of acoustic parameters must be perceptually discretized by the auditory system. Such many-to-one mappings of undifferentiated sensory information to a finite number of discrete categories are ubiquitous in perception. Although many mechanistic models of phonetic perception have been proposed, they remain largely unconstrained by neurobiological data. Current human neurophysiological methods lack the necessary spatiotemporal resolution to provide it: speech is too fast, and the neural circuitry involved is too small. This study demonstrates that mice are capable of learning generalizable phonetic categories, and can thus serve as a model for phonetic perception. Mice learned to discriminate consonants and generalized consonant identity across novel vowel contexts and speakers, consistent with true category learning. A mouse model, given the powerful genetic and electrophysiological tools for probing neural circuits available for them, has the potential to powerfully augment a mechanistic understanding of phonetic perception.

Studying the rate of velar elevation across different vowel contexts in normal speech using high speed nasopharyngoscopy

Velum has a range of positions across different speech segments, with the lowest velum position for nasal consonants, a high (closed) position for obstruent consonants, and a range of positions in the middle for sonorant consonants and vowels varying according to constriction degree. Vowel environment has a considerable influence on the rate of velum closure. Changes in the rates of velar positioning during production of vowels in non-nasal speech (H-words) was studied in seven typically speaking adults with general American dialect and normal oral-nasal resonance. The participants were scoped using a Phantom Miro 310 high-speed video camera (Image acquisition rate of 5000 fps) connected to a flexible scope. Measurements were taken simultaneously with capturing acoustic data. The data suggested that velum tends to have a higher elevation point for vowels with higher degree of constriction in the oral cavity like /i/. Further results will be discussed.

Prevoicing and prenasalization in Russian initial plosives

This study investigated the production of prevoiced initial plosives in Russian, including examining (i) how closure voicing varies depending on consonantal place, vocal context and speaker gender and (ii) whether Russian speakers rely on prenasalization to produce vocal fold vibration in initial closures, which is one of the mechanisms of reducing supraglottal pressure during oral occlusion. The study analyzed acoustic and airflow data from large samples of speakers and stimulus items, which made it possible to examine group-level patterns. Results for prevoicing duration revealed an effect of consonantal posteriority and adjacent vowel height. Shorter durations were seen in velars than bilabials or dentals and in tokens with high vowels (especially in male speech). Prevoiced tokens also showed higher levels of nasal flow than voiceless plosives during the initial part of closure. Nasal flow levels were lower in bilabials than dentals or velars and were not affected by vowel context. Speaker gender influenced voiceless tokens only. Towards the end of closure, voiced and voiceless tokens demonstrated comparable nasal flow levels. These results provide new insights into prevoicing in Russian and the link between prevoicing and prenasalization.

The articulation of /ɹ/ in New Zealand English

This paper investigates the articulation of approximant /ɹ/ in New Zealand English (NZE), and tests whether the patterns documented for rhotic varieties of English hold in a non-rhotic dialect. Midsagittal ultrasound data for 62 speakers producing 13 tokens of /ɹ/ in various phonetic environments were categorized according to the taxonomy by Delattre & Freeman (1968), and semi-automatically traced and quantified using the AAA software (Articulate Instruments Ltd. 2012) and a Modified Curvature Index (MCI; Dawson, Tiede & Whalen 2016). Twenty-five NZE speakers produced tip-down /ɹ/ exclusively, 12 tip-up /ɹ/ exclusively, and 25 produced both, partially depending on context. Those speakers who produced both variants used the most tip-down /ɹ/ in front vowel contexts, the most tip-up /ɹ/ in back vowel contexts, and varying rates in low central vowel contexts. The NZE speakers produced tip-up /ɹ/ most often in word-initial position, followed by intervocalic, then coronal, and least often in velar contexts. The results indicate that the allophonic variation patterns of /ɹ/ in NZE are similar to those of American English (Mielke, Baker & Archangeli 2010, 2016). We show that MCI values can be used to facilitate /ɹ/ gesture classification; linear mixed-effects models fit on the MCI values of manually categorized tongue contours show significant differences between all but two of Delattre & Freeman's (1968) tongue types. Overall, the results support theories of modular speech motor control with articulation strategies evolving from local rather than global optimization processes, and a mechanical model of rhotic variation (see Stavness et al. 2012).

Effect of vowel context in cepstral and entropy analysis of pathological voices

This study investigates the effect of vowel context (excerpted from speech versus sustained) on two voice quality measures: the cepstral peak prominence smoothed (CPPS) and sample entropy (SampEn). ...

Articulatory and acoustic investigations into gestures of Mandarin retroflex fricatives

This study investigates the inventory and acoustic realizations of articulatory gestures of the Mandarin retroflex (or arguably, post-alveolar) fricative /ʂ/. Tongue shapes were obtained with ultrasound images and categorized as retroflexed or bunched, in light of the literature on the North American English rhotic /ɹ/ production. Velarization, a secondary articulatory gesture of retroflex consonants, was also coded in the ultrasound imaging analysis. Lip rounding, found to be an optional enhancing gesture in Mandarin retroflexion, was identified with lip video data. The acoustic measurements included the spectral center of gravity obtained from the middle of the frication and F2 frequency measured at the onset of the vowel following the fricative. The analyses showed that the spectral center of gravity only varied as a function of the vowel context. F2 at vowel onset was affected by vowel context, velarization and the interaction of vowel context and lip rounding. The preliminary results failed to support previous speculations that the two tongue shapes in Mandarin retroflexes result in different acoustics. We consider including more acoustic measures to further explore the acoustic consequences of articulatory variations in Mandarin retroflex fricatives.This study investigates the inventory and acoustic realizations of articulatory gestures of the Mandarin retroflex (or arguably, post-alveolar) fricative /ʂ/. Tongue shapes were obtained with ultrasound images and categorized as retroflexed or bunched, in light of the literature on the North American English rhotic /ɹ/ production. Velarization, a secondary articulatory gesture of retroflex consonants, was also coded in the ultrasound imaging analysis. Lip rounding, found to be an optional enhancing gesture in Mandarin retroflexion, was identified with lip video data. The acoustic measurements included the spectral center of gravity obtained from the middle of the frication and F2 frequency measured at the onset of the vowel following the fricative. The analyses showed that the spectral center of gravity only varied as a function of the vowel context. F2 at vowel onset was affected by vowel context, velarization and the interaction of vowel context and lip rounding. The preliminary results failed to suppor...

Acoustic and articulatory evidence on incomplete syllable-final nasal mergers in Taiwan Mandarin

Previous studies reported that syllable-final nasals in Taiwan Mandarin, /n/ and /ŋ/, exhibit merging to different degrees in the vowel contexts of /i/ and /ə/ (e.g., Ing 1985, Kubler 1985, Hsu & Tse 2007, Fon et al., 2011). However, the discussion has been mainly on the merging directions, ethnic groups that display the mergers, and attitudes towards the different merging directions. Apart from the large evidence of merging from perceptual identification of the final nasal, this study employs ultrasound imaging technique to examine tongue postures of the syllable-final nasal following /i, a, ə/ vowel contexts. Preliminary results showed that /n/ and /ŋ/ were distinct both acoustically and articulatorily in the context of /a/, echoing earlier findings (e.g., Fon et al., 2011). On the other hand, while the contours of tongue shapes demonstrate extensive overlapping between /n/ and /ŋ/ following /i/ and /ə/, their correspondent acoustics display different degrees of nasalization on the preceding vowels (cf. Chen, 2000). More generally, the results suggest that the merging in syllable-final nasals undergoes an incomplete process and the acoustic contrasts might have lie in the nasalization of the preceding vowels and less so in syllable-final nasals.Previous studies reported that syllable-final nasals in Taiwan Mandarin, /n/ and /ŋ/, exhibit merging to different degrees in the vowel contexts of /i/ and /ə/ (e.g., Ing 1985, Kubler 1985, Hsu & Tse 2007, Fon et al., 2011). However, the discussion has been mainly on the merging directions, ethnic groups that display the mergers, and attitudes towards the different merging directions. Apart from the large evidence of merging from perceptual identification of the final nasal, this study employs ultrasound imaging technique to examine tongue postures of the syllable-final nasal following /i, a, ə/ vowel contexts. Preliminary results showed that /n/ and /ŋ/ were distinct both acoustically and articulatorily in the context of /a/, echoing earlier findings (e.g., Fon et al., 2011). On the other hand, while the contours of tongue shapes demonstrate extensive overlapping between /n/ and /ŋ/ following /i/ and /ə/, their correspondent acoustics display different degrees of nasalization on the preceding vowels (cf....

Developing new pre-lexical processing skills in adults

Studies of adults learning to decode words may provide a window on understanding of the pre-lexical processing of words as learning progresses. Second language (L2) learners (for example) have been found to assimilate new phones to first language (L1) phonemes when asked for the closest sound in their languages (e.g., Schmidt, 1996). Ratings of fit with L1 phonemes was related to details of acoustics of stimuli, L1 acoustics, and vowel context suggesting that L1 phonetic details rather than phoneme categories were compared. What happens after attention has been focused on acoustic/articulatory characteristics of these new sounds (as in training studies) and learning progresses? Do adults establish new phoneme categories to aid in word processing or is it more likely that native categories are expanded based upon developing within L1 category perceptual skills and orthographic word prediction skills. Evidence will be reviewed indicating that learned production of L2 sounds can be become native-like but L2 perception outcomes remain non-native like suggesting that new phoneme categories are not formed. Thus, new learned words can be accurately produced but success in pre-lexical processing of new heard words will depend upon linguistic factors such as context.

Restrições linguísticas na palatalização do /s/ pós-vocálico seguido de [t] ou [ʧ] na fala de Caravelas – Bahia

Neste texto, apresentamos generalizações sobre efeitos linguísticos na realização alveopalatal [ʃ] ou alveolar [s] do /S/ pós-vocálico seguido de [t] ou [ʧ] na fala de 25 falantes de Caravelas-BA, estratificados pelo sexo, faixa etária e escolarização. A análise foi feita à luz da Teoria da Variação e Mudança Linguística (LABOV, 2008 [1972]; WEINREICH, LABOV & HERZOG, 2006 [1968]). Para o tratamento estatístico dos 1189 dados variáveis, usamos o GoldVarb X (SANKOFF, TAGLIAMONTE & SMITH, 2005). A primeira restrição estatisticamente significativa é a posição do /S/ na palavra, com a posição medial favorecendo a palatalização. A segunda é o contexto vocálico antecedente, em que a palatalização é favorecida pelos traços [+posterior] e [+alto]: o efeito mais forte é da vogal [u]. A posteriorização é o traço de maior influência, paralelamente ao efeito da vogal alta anterior [i]. Portanto, quanto mais recuada e mais alta a língua na vogal antecedente, maior a chance da realização alveopalatal. A terceira restrição estatisticamente significativa é o contexto consonantal seguinte, em que a alveopalatal é favorecida pela africada alveopalatal [ʧ] e inibida pela oclusiva alveolar [t]. Desse modo, propriedades de segmentos precedentes e seguintes evidenciam assimilação progressiva e regressiva, respectivamente, caracterizando um fenômeno linguístico regular.

Oropharygneal articulation of phonemic and phonetic nasalization in Brazilian Portuguese

The phonological feature [±nasal] does not distinguish systematic oropharyngeal differences between oral, nasal, and phonetically nasalized vowels. A variety of studies now show that oropharyngeal shape may systematically enhance or compensate for the acoustic effects of nasal coupling. Additionally, the phonetic implementation of [−nasal] vowels in oral and nasal contexts is a matter of some controversy. While the velopharyngeal opening of these vowels has been inferred from aerodynamics, we know of no attempt to directly study the oropharyngeal articulation of underlyingly oral vowels in nasal and oral contexts in a language that may also have phonemically [+nasal] vowels. In this study, real-time magnetic resonance imaging (rt-MRI) is used to study vocal tract configuration in Brazilian Portuguese (BP), a language that arguably has [+nasal] (phonemically nasal) vowels and two classes of [−nasal] vowels (oral and phonetically nasalized). Results show oropharyngeal differences between nasal and oral vowel congeners /a∼ã/, /i∼ĩ/ and /u∼ũ/, which arguably enhance well-known acoustic effects of nasal coupling on vowel height. In addition, nasal coda consonants emerge following nasal vowels. Phonetically nasalized vowels, on the other hand, show no sign of nasal enhancement, including nasal coda emergence, implying they are underlyingly oral vowels, despite the environment in which they occur. We argue that nasal vowels in BP are underlyingly /Ṽ/, rather than /VN/ sequences, the latter distinction being reserved for nasalized vowels. Articulatory divergence of [+nasal] and [−nasal] vowels has implications in perception, sound change, and the phonetic implementation of nasality.

The gradient influence of temporal extent of coarticulation on vowel and speaker perception

Coarticulation makes vowels in context acoustically different from context-free vowels. Listeners sometimes compensate by ascribing these acoustic effects to their source, but the conditions under which they do so have not yet been fully pinpointed. Ohala (1993) had suggested that acoustic effects which are temporally more distant from their source should be more susceptible to misattribution. In three experiments, we tested this hypothesis by varying the temporal extent of coda-triggered coarticulation on vowels and investigating its influence on two different perceptual behaviors: speaker-model representation and vowel-phoneme identification. Experiment 1 asked listeners to estimate speaker height based on /giC/ and /gɪC/ nonsense tokens produced by twelve female speakers. Results indicated a gradient effect: Within lax /ɪ/, greater temporal extent of coarticulation correlated with taller height judgments. Experiment 2a was similar, except that temporal extent of coarticulation in the tokens varied across a wider range of values than in Experiment 1. Results again indicated a gradient effect: Within lax /ɪ/, greater temporal extent of coarticulation correlated with taller height judgments. In Experiment 2b, listeners performed an AXB vowel-phoneme discrimination task. Results showed that greater temporal extent of coarticulation correlated with greater likelihood of listeners judging an intended /ɪ/ token to contain the vowel /ʌ/. Taken together, our results indicate that temporal extent of coarticulation affects both speaker-models and interpretation of vowel identity.

Quantifying robustness of the /t/-/k/ contrast using a single, static spectral feature

Dynamic spectral shape features accurately classify /t/ and /k/ productions across speakers and contexts. This paper shows that word-initial /t/ and /k/ tokens produced by 21 adults can be differentiated using a single, static spectral feature when spectral energy concentration is considered relative to expectations within a given speaker and vowel context. Centroid and peak frequency-calculated from both acoustic and psychoacoustic spectra-were compared to determine whether one feature could reliably differentiate /t/ and /k/, and, if so, which feature best differentiated them. Centroid frequency from both acoustic and psychoacoustic spectra accurately classified productions of /t/ and /k/.

Effects of vowel context and discriminability on band independence in nonsense syllable recognition.

The Speech Intelligibility Index algorithm [(1997). ANSI S3.5-1997] models cues in disjoint frequency bands for consonants and vowels as additive, independent contributions to intelligibility. Data from other studies examining only consonants in single-vowel nonsense stimuli exhibit synergetic and redundant band contributions that challenge the band independence assumption. The present study tested the hypotheses that (a) band independence is present for multi-vowel stimuli, and (b) dependent band contributions are artifacts of confounding stimulus administration and testing methods. Data were measured in two experiments in which subjects identified filtered nonsense consonant-vowel-consonant syllables using a variety of randomly selected vowels. The measured data were used in simulations that further characterized the range of subject responses. Results of testing and simulation suggest that, where present, band independence is fostered by low broadband error, high vowel diversity, and high vowel discriminability. Synergistic band contributions were observed for confusable vowels that were most susceptible to filtering; redundant contributions were observed for the least susceptible vowels. Implications for intelligibility prediction and enhancement are discussed.

Backward masking of tones and speech in people who do and do not stutter

PurposeThere is evidence of an auditory-perceptual component of stuttering, and backward masking (BM) is a task to explore that role. Prior research reported poorer thresholds for BM tones in a group of children who persisted in stuttering compared to those for a group that did not persist. This study examined BM for adults who stutter for tones and for speech, which tests a phonetic aspect of hearing. MethodEight persons who stutter (PWS) were closely matched with eight controls (PNS) in terms of phonological abilities, verbal span tasks, age, sex and non-verbal intelligence. These participants were examined for their ability to recognize vowel-consonant (VC) speech syllables and tones in BM paradigm with 0 ms and 300 ms masker to signal onset conditions. ResultsPWS showed significantly poorer performance for speech syllable recognition in quiet and in conditions with masking noise. The pattern of speech errors was similar in both groups, but the PWS produced more errors. A significant condition by group interaction in backward masking for tones was attributed to higher masked thresholds in PWS than in PNS in the 0 ms delay condition for BM for tones. ConclusionThis was the first study to examine BM for speech in PWS. Results provide support for a small auditory-perceptual deficit for speech understanding in adults who stutter that was revealed in the absence of a lexical context. The speech results are explained in terms of possible indistinct phoneme boundaries in PWS and the effects of vowel context in speech recognition.

Recognition of Spanish consonants in 8-talker babble by children with cochlear implants, and by children and adults with normal hearing.

This paper presents the results of closed-set recognition task for 80 Spanish consonant-vowel sounds in 8-talker babble. Three groups of subjects participated in the study: a group of children using cochlear implants (CIs; age range: 7-13), an age-matched group of children with normal hearing (NH), and a group of adults with NH. The speech-to-noise ratios at which the participants recognized 33% of the target consonants were +7.8 dB, -3 dB, and -6 dB, respectively. In order to clarify the qualitative differences between the groups, groups were matched for the percentage of recognized syllables. As compared with the two groups with NH, the children with CIs: (1) produced few "I do not know" responses; (2) frequently selected the voiced stops (i.e., /b, d, ɡ/) and the most energetic consonants (i.e., /l, r, ʝ, s, ʧ/); (3) showed no vowel context effects; and (4) had a robust voicing bias. As compared with the adults with NH, both groups of children showed a fronting bias in place of articulation errors. The factors underlying these error patterns are discussed.

Development of fricative sound perception in Korean infants: The role of language experience and infants’ initial sensitivity

In this paper, we report data on the development of Korean infants’ perception of a rare fricative phoneme distinction. Korean fricative consonants have received much interest in the linguistic community due to the language’s distinct categorization of sounds. Unlike many fricative contrasts utilized in most of the world’s languages, Korean fricatives (/s*/-/s/) are all voiceless. Moreover, compared with other sound categories, fricatives have received very little attention in the speech perception development field and no studies thus far have examined Korean infants’ development of native phonology in this domain. Using a visual habituation paradigm, we tested 4‒6-month-old and 7‒9-month-old Korean infants on their abilities to discriminate the Korean fricative pair in the [a] vowel context, /s*a/-/sa/, which can be distinguished based on acoustic cues, such as the durations of aspiration and frication noise. Korean infants older than 7 months were able to reliably discriminate the fricative pair but younger infants did not show clear signs of such discrimination. These results add to the growing evidence that there are native sound contrasts infants cannot discriminate early on without a certain amount of language exposure, providing further data to help delineate the specific nature of early perceptual capacity.