Production Of Stop Consonants Research Articles

Control of oral closure in lingual stop consonant production.

Previous work has shown that the lips are moving at a high velocity when the oral closure occurs for bilabial stop consonants, resulting in tissue compression and mechanical interactions between the lips. The present experiment recorded tongue movements in four subjects during the production of velar and alveolar stop consonants to examine kinematic events before, during, and after the stop closure. The results show that, similar to the lips, the tongue is often moving at a high velocity at the onset of closure. The tongue movements were more complex, with both horizontal and vertical components. Movement velocity at closure and release were influenced by both the preceding and the following vowel. During the period of oral closure, the tongue moved through a trajectory of usually less than 1 cm; again, the magnitude of the movement was context dependent. Overall, the tongue moved in forward-backward curved paths. The results are compatible with the idea that the tongue is free to move during the closure as long as an airtight seal is maintained. A new interpretation of the curved movement paths of the tongue in speech is also proposed. This interpretation is based on the principle of cost minimization that has been successfully applied in the study of hand movements in reaching.

Aspects of Stop Consonant Production by Pediatric Users of Cochlear Implants.

Data and analyses are reported for stop consonant production by 12 children who have used cochlear implants for at least 5 years, focusing on variation within and between individual phonological systems. Participants were 6 oral communication users and 6 total communication users. Productions of single words were analyzed for stop inventories, phonotactic constraints, and morphophonemic alternations. Variation was further analyzed within optimality theory. Children's inventories differed from English mainly in having additional, non-English stops. Total communication users had fewer ambient stops and more nonambient ones than did oral communication users. Control over English allophonic and neutralization rules varied among children. Phonological variation could be accounted for by positing unique underlying representations and different constraint rankings within optimality theory. Atypical speech by children with cochlear implants involves both articulation and phonological organization. Although children vary considerably, characteristic patterns emerge. An understanding of these patterns is useful for identifying areas of difficulty and formulating intervention programs.

The influence of speaking rate on spirantization in motor speech disorders

Spirantization occurs often in the speech of individuals with dysarthria. Impairment of muscle movement can lead to an incomplete articulatory obstruction of the vocal tract during the closure period for the production of stop consonants. Air passes through the narrow constriction associated with the incomplete constriction, resulting in the production of fricative noise during the stop gap. This noise leads to the perception of imprecise articulation. It is hypothesized that the speaking rate at which an individual with dysarthria talks will influence the frequency of spirantization. The slower the speaking rate the more time is allowed for the speaker with dysarthria to achieve a tight constriction during the closure period for stop production, resulting in a reduction of spirantization. The opposite would occur for faster rates. For this experiment, individuals with dysarthria read the Farm Passage at three different speaking rates (hab, slow & fast). From this passage, the production of initial voiceless stop consonants (/p, t & k/) were analyzed for the presence of frication during the closure period. Statistical comparisons were made across speaking rate and place of production. group and individual results will be presented.

Respiratory Responses to Sudden Pressure Venting during Stop Consonant Production

Twenty healthy adults, age range 20–55 years, participated in a study to assess the responses of the upper airway to sudden, unanticipated pressure venting during speech production. A computer was used to open or close a valve in a random fashion during one of two productions of the word ‘hamper’. The SAR System (Microtronics Corp., Chapel Hill, N.C., USA) was used to collect and monitor respiratory variables associated with speech production. Results indicated no significant changes in duration between vented and unvented conditions. Although intraoral pressure was reduced under vented conditions, the magnitude was sufficient for sound generation. Respiratory effort increased when the airway was suddenly vented, suggesting a compensatory response to experimental perturbation. However, the response contrasted somewhat from what has been observed in patients with velopharyngeal inadequacy, indicating that the strategy used may be different.

Control of oral closure in stop consonants with different closure durations

This study examined lip and tongue kinematics in the production of stop consonants that differ in the duration of the oral closure. The linguistic material consisted of Swedish words that contained either a short vowel followed by a long stop, or a long vowel followed by a short stop. Articulatory movements were recorded using a magnetometer system. The average closure duration for the long stops was 100–150 ms, about twice the closure duration for the short stops. Preliminary results for one subject suggest that the lip closure for the long stop was produced with an upward movement trajectory of the lower lip that reached a higher position during the closure than the trajectory for the stop with a short oral closure. As a result, there was more mechanical interaction between the upper and lower lips, with the lower lip pushing the upper lip upward. For stops articulated with the tongue, the tongue moved along a longer path during the stop closure for the long than for the short stops. The average velocity of the tongue movement during the stop closure was lower for the long than for the short stops. [Work supported by NIH.]

VCV synthesis from muscle commands

The biomechanical model of the tongue developed by Payan and Perrier [Speech Commun. 22, 185–205 (1997)] is used to generate tongue movements in VCV sequences, where V is [i], [a], or [u] and C is the stop consonant [k]. Tissues’ elastic properties are accounted for in finite-element modeling, and the mechanisms underlying the production of muscle forces are modeled according to Feldman’s Equilibrium Point Hypothesis. Each elementary sound is associated with a target that is described as a static equilibrium position of the tongue, which is likely to vary with the phonemic context. In vowel production, the target is actually supposed to be reached, while the production of stop consonants consists of movements toward virtual targets located beyond the palate, which therefore cannot be reached. The collision of the tongue against the palate is modeled according to a penalty method, based on a nonlinear relationship between contact force and position/velocity of points located on the tongue surface [Marhefka and Orin, IEEE Conf. Robotics and Automation, 1662–1668 (1996)]. The acoustic signal is generated with a one-dimensional low-frequency approximation based on the Kelly–Lochbaum model. Synthetic kinematic and acoustic signals are compared with human speakers’ data. [Work supported by CNRS, NSF, and NIH.]

On the relevance of locus equations for production and perception of stop consonants.

We examined the possible relevance of locus equations to human production and perception of stop consonants. The orderly output constraint (OOC) of Sussman, Fruchter, and Cable (1995) claims that humans have evolved to produce speech such that F2 at consonant release and F2 at vowel midpoint are linearly related for consonants so that developing perceptual systems can form representations in an F2ons-by-F2vowel space. The theory claims that this relationship described by locus equations can distinguish consonants, and that the linearity of locus equations is captured in neural representations and is thus perceptually relevant. We investigated these claims by testing how closely locus equations reflect the production and perception of stop consonants. In Experiment 1, we induced speakers to change their locus equation slope and intercept parameters systematically, but found that consonants remained distinctive in slope-by-intercept space. In Experiment 2, we presented stop-consonant syllables with their bursts removed to listeners, and compared their classification error matrices with the predictions of a model using locus equation prototypes and with those of an exemplar-based model that uses F2ons and F2vowel, but not locus equations. Both models failed to account for a large proportion of the variance in listeners' responses; the locus equation model was no better in its predictions than the exemplar model. These findings are discussed in the context of the OOC.

Lip and jaw kinematics in bilabial stop consonant production.

This paper reports two experiments, each designed to clarify different aspects of bilabial stop consonant production. The first one examined events during the labial closure using kinematic recordings in combination with records of oral air pressure and force of labial contact. The results of this experiment suggested that the lips were moving at a high velocity when the oral closure occurred. They also indicated mechanical interactions between the lips during the closure, including tissue compression and the lower lip moving the upper lip upward. The second experiment studied patterns of upper and lower lip interactions, movement variability within and across speakers, and the effects on lip and jaw kinematics of stop consonant voicing and vowel context. Again, the results showed that the lips were moving at a high velocity at the onset of the oral closure. No consistent influences of stop consonant voicing were observed on lip and jaw kinematics in five subjects, nor on a derived measure of lip aperture. The overall results are compatible with the hypothesis that one target for the lips in bilabial stop production is a region of negative lip aperture. A negative lip aperture implies that to reach their virtual target, the lips would have to move beyond each other. Such a control strategy would ensure that the lips will form an air light seal irrespective of any contextual variability in the onset positions of their closing movements.

Control of oral closure in alveolar and velar stop consonant production

Earlier work has shown that the lips are moving at a high velocity at the instant of oral closure for bilabial stop consonants, resulting in tissue compression. The lips may thus have virtual targets that would require them to move beyond each other. The present study examines events at the oral closure for stops produced with the tongue. Tongue movements were recorded using a magnetometer system. Four subjects participated and produced ten tokens each of VCV sequences with all possible combinations of the three vowels /i, a, u/ and the consonants /t, d, k, g/. Consistent with the results for bilabial stops, the tongue was moving at a high velocity at the instant of oral closure. The tongue movement trajectories were more complex with a larger horizontal component than the lips. For velar stops, the tongue body was usually moving forward at stop closure, with the velocity influenced by vowel context. For alveolar stops, the tongue tip horizontal movement direction depended on the preceding vowel, but also differed across subjects. Between the onset and release of the oral closure, the tongue tip and tongue body moved through a trajectory of usually less than 1 cm. [Work supported by NIH.]

Effects of speaking rate on voice-onset time in Thai, French, and English

This study investigated the effect of speaking rate on stop consonant production in three languages which have different phonetic categories of voicing. Voice-onset time (VOT) distributions and mean VOT values were examined for initial labial and alveolar stop consonants produced in CV(C) words in isolation and in context at both slow and fast rates of speech. Results revealed that the short lag category did not change as a function of speaking rate in any of the three languages examined, although VOT values for long lag (Thai and English) and pre-voiced (Thai and French) stop consonants were affected by changes in speaking rate. However, the shift of the long lag and pre-voiced categories toward the short lag VOT values in the fast rate condition resulted in little overlap between voicing categories. Implications of these results for the nature of phonetic categories are discussed.

Voice onset time of Japanese and English stop consonants uttered by the returnees (Japanese–English bilinguals)

The present study deals with the speech production by bilinguals in both languages. The objective speech sounds are Japanese and English stop consonants. Japanese stop consonants are very similar to English ones, but is is well-known that the voice onset time of stop consonants for both languages are different from one another. The aim of this study is to examine the voice onset time of Japanese and English stop consonants uttered by the returnees (Japanese–English bilinguals) under the different linguistic circumstances. It was found that there were three types for the returnees in the production of stop consonants. These results are compared with those of Japanese who learned English.

Control of the oral release in bilabial stop consonant production

This study examines kinematic patterns of lip and jaw movements in bilabial stop production at the release of the oral closure. Lip and jaw movements were recorded using a magnetometer system. Five subjects participated and produced 50 tokens of the sequences /aCV/, where C was either /p/ or /b/ and V one of /i, a, u/. The organization of jaw movements differed between subjects. In two of the subjects, the jaw did not reach any peak position during the stop but moved continuously during the stop to a peak position during the following vowel; this was the case when the second vowel was one of /i, u/. The open vowel /a/ was reliably associated with a jaw lowering movement of greater amplitude and velocity than the vowels /i, u/. The onset of the lower lip release movement generally occurred before the onset of the jaw lowering movement. The peak velocity of both the lower lip and jaw release movement sometimes occurred before the release of the oral closure. Stop consonant voicing had no consistent influence on the release movements of the lips and the jaw, nor on a derived measure of lip aperture. [Work supported by NIH.]

Labial kinematics in stop consonant production.

This study examines kinematic patterns of upper and lower lip movements in bilabial stop production with particular emphasis on events before and during the oral closure. Lip movements were recorded using a magnetometer system. Five subjects participated and produced 50 tokens of the sequences /aCV/, where C was either /p/ or /b/ and V one of the vowels /i, a, u/. Force of labial contact and oral air pressure were also recorded in one subject. The results indicate that at the instant of oral closure, the velocity of both lips was close to peak velocity. They also show that the lower lip continued its upward movement after oral closure. This was reflected in the force of labial contact, which showed an increase in contact pressure after the oral closure had occurred. During the period of lower lip upward movement after the oral closure, the upper lip often showed a corresponding upward movement, suggesting that the lower lip might be pushing the upper lip. These results support the hypothesis that one goal in making the lip closure is a region of negative lip aperture. [Work supported by NIH.]

Control of lip closure in stop consonant production

Studies applying mechanical perturbations to the lower lip and the jaw have shown a trade off between movements of perturbed and unperturbed articulators in making the lip closure for a bilabial stop. While this concept is attractive, evidence for such trading relationships in normal speech has remained elusive, partly due to methodological problems. This study examines the vertical positions of the upper and lower lip at closure for bilabial stops. An electromagnetic transduction system was used to track receivers on the upper and lower lips, and the lower incisors for transducing jaw movements. The speech material consisted of VCV sequences where the first vowel was /a/, the middle consonant /p,b/, and the second vowel /i,a/; stress occurred on the second vowel. Preliminary results from three subjects showed upper lip positions at closure to occur over a range of 0.3 cm; the range for lower lip positions was 0.5 cm. Examination of 40 tokens for each subject revealed a positive relationship between upper and lower lip positions at closure, with correlation coefficients ranging from 0.5 to 0.7. The results will be discussed in relation to theories of speech motor control. [Work supported by NIH.]

Underlying control strategies for the production of stop consonants

The underlying control strategies utilized in the production of stop consonants were investigated using an electromagnetic midsagittal articulometer [J. Perkell etal., J. Acoust. Soc. Am. 92, 3078–3096 (1992)]. The movements in the midsagittal plane of points on the lower jaw, lips, tongue blade, and tongue body were measured for three normal hearing, normal speaking subjects during the production of single-syllable words composed of a stop or nasal consonant followed by the vowel /ɑ / or /i/ and the consonant /t/, and spoken in a carrier phrase. Half the tokens were preceded by the fricative consonant /s/. The data show that the maximum downward velocity of the lower jaw occurs approximately at the time of the consonant release. For /sCV/ syllables, the lower jaw is held in a high position to assist in noise generation for /s/, and consequently the movement for a following labial or velar consonant follows a time course that is different from that of /CV/ syllables. The movement of the articulators during the production of these utterances at a normal speaking rate appears to have a bandwidth limitation of 5–7 Hz. [Work supported in part by grants from NIDCD.]

Models for the production and acoustics of stop consonants

Stop consonants are produced by forming a closure in the vocal tract, building up pressure in the mouth behind this closure, and releasing the closure. Models of the mechanical, aerodynamic, and acoustic events in the vicinity of the stop consonant are described, and examples of calculations of the airflow and of various components of the radiated sound are given. At the consonantal release, these components of the sound include an initial transient, a burst of frication noise, and an interval in which there is a sound source at the glottis and transitions in the formants. The models predict the absolute levels of these components for different places of articulation for the consonants.

Speaking Rate and Speech Movement Velocity Profiles

The effects of speaking rate on the velocity profiles of movements of the lower lip and tongue tip during the production of stop consonants were examined using an x-ray microbeam system. Five young adults used a magnitude production task to produce five speaking rates that ranged from very fast to very slow. Results indicated that changes in speaking rate were associated with changes in the topology of the speech movement velocity-time function. Specifically, the velocity profile changed from a symmetrical, single-peaked function at the fast speaking rates to an asymmetrical and multi-peaked function at the slow speaking rates. This variation in velocity profile shape is interpreted as support for the view that alterations in speaking rate are associated with changes in motor control strategies. In particular, the control strategy for speech gestures produced at fast speaking rates appears to involve unitary movements that may be predominantly preprogrammed, whereas gestures produced at slow speaking rates consist of multiple submovements that may be influenced by feedback mechanisms.

Acoustic properties contributing to the classification of place of articulation for stops.

The production of stop consonants generates several kinds of acoustic properties: (i) the spectrum of the initial transient and burst indicating the size of the cavity anterior to the constriction; (ii) place-dependent articulatory dynamics leading to different time courses of the noise burst, onset of glottal vibrations and formant transitions; (iii) formant transitions indicating the changing vocal tract shape from the closed position of the stop to a more open configuration of the following vowel. The interest in this study is to measure the relative contributions of these acoustic properties to the classification of the consonantal place of articulation using a semi-automatic procedure. The acoustic data consisted of a number of repetitions of voiceless unaspirated stops in meaningful words spoken by several female and male speakers. The spectra averaged over the stop release and at the vowel onset were used as the acoustic feature. Speaker-independent and vowel-independent classification was about 80% using either the burst or vowel onset spectrum and a combined strategy led to a higher accuracy. Studies with additional acoustic properties that relate to articulatory dynamics, such as VOT and formant transitions, are planned.

Articulatory deficits in parkinsonian dysarthria: an acoustic analysis.

Twelve patients with idiopathic Parkinson's disease had acoustic speech analysis of sentence utterances to provide information on speech tempo and accuracy of articulation. As a measure of rate of speech the duration of opening-closing movements during articulation was determined from speech wave variables. The intensity of sound emission during articulatory closure as required for stop consonant production, for example, magnitude of p, magnitude of t, magnitude of k, was used as an index of the degree of closure. Speech tempo was not significantly different from normal. The patients, however, had a reduced capacity of completing articulatory occlusion. This was interpreted as reflecting a reduction in movement amplitude of the articulators. Articulatory "undershoot" was not uniform but influenced by linguistic demands in that the closures associated with a stressed syllable were performed at the expense of unstressed ones. Furthermore, switching between opening and closing movements of the articulators in sentence production seemed undisturbed. These results indicate that motor planning of speech differs from arm movement control.

Aspects of final consonant production in American English by nonnative speakers.

This paper describes the production of word-final, utterance-medial /t, d/ in American English by native speakers and by three groups of nonnative speakers of English. Twenty-four nonnative subjects, whose native languages include Arabic, Korean, Spanish, and Thai, were rated by native English speakers as having no accent, a mild accent, or a medium to heavy accent in English. Measurement of five tokens each of /t/ and /d/ for each speaker and for 6 native English speakers were compared. Neither the Americans nor any of the nonnative groups significantly differentiated /t/ from /d/ by closure duration. As strength of accent rating increased, mean closure duration tended to increase. Also, as strength of accent rating increased, implementation of manner of stop consonant production (including flapping and aspirated versus nonaspirated release) tended to change. Results suggest that both duration and the ability to produce a number of durationally different release options in English may affect the degree of perceived foreignness.