Vocal Tract Constriction Research Articles

An articulatory-acoustic-aerodynamic analysisof [s] in VCV sequences

Previous studies of the effect of vowel context on fricatives showseeming contradictions in the case of /s/: acoustic analysis shows the greatest context effect, while aerodynamic analysis shows relatively little effect, for the same subject. In this study, aerodynamic, acoustic, and articulatory data for the same subject producing /s, z/ in a variety of contexts were compared systematically. The strong acoustic effect of the /u - u/ context exists with /z/ as well as /s/, and appears to arise from a whistle-like source mechanism caused by lip rounding; the main tongue constriction does appear to be immune to vowel context. Our interpretation of aerodynamic data as constrictions in series can be generalized to include the influence of lip rounding, thus: for this speaker and for these speech-like sequences, the area of the vocal tract constriction for /s/ is independent of the vowel context but the overall aerodynamic effect does vary with lip rounding. Our aerodynamic and acoustic data seem to be consistent; both support the view that some rounding extends into the /s/ fricative.

Trade-offs in tongue, jaw, and palatecontributions to speech production

This study examined the interarticulatory behaviors of the tongue,jaw, and palate. The effects of the vowels [i] and [α] on the consonants [l] and [s] were studied using electropalatography (EPG), Selspot, and Ultrasound imaging. Three subjects repeated [ilila], [alol∂], [isis∂], and [asas∂] five times each. Tongue-palate contact patterns, jaw position, and cross-sectional tongue surface profiles were measured. Results indicated that assimilation effects on one articulator could elicit compensatory maneuvers in a related articulator to assure that key articulators reached their target. This effect was similar to compensatory maneuvers resulting from experimentally-induced jaw perturbations. The study also was able to represent the vocal tract constriction with just two degrees of freedom: shape and openness. Finally, if the jaw was moderately high, tongue shape and EPG pattern relationships could be determined.

Acoustic and perceptual effects of changes in vocal tract constrictions for vowels

The purpose of this study was to use vocal tract simulation and synthesis as means to determine the acoustic and perceptual effects of changing both the cross-sectional area and location of vocal tract constrictions for six different vowels: Area functions at and near vocal tract constrictions are considered critical to the acoustic output and are also the central point of hypotheses concerning speech targets. Area functions for the six vowels, [symbol: see text] were perturbed by changing the cross-sectional area of the constriction (Ac) and the location of the constriction (Xc). Perturbations for Ac were performed for different values of Xc, producing several series of acoustic continua for the different vowels. Acoustic simulations for the different area functions were made using a frequency domain model of the vocal tract. Each simulated vowel was then synthesized as a 1-s duration steady-state segment. The phoneme boundaries of the perturbed synthesized vowels were determined by formal perception tests. Results of the perturbation analyses showed that formants for each of the vowels were more sensitive to changes in constriction cross-sectional area than changes in constriction location. Vowel perception, however, was highly resistant to both types of changes. Results are discussed in terms of articulatory precision and constriction-related speech production strategies.

Vocal Tract Area Function Estimation From Midsagittal Dimensions With CT Scans and a Vocal Tract Cast

The generation of area functions from measurements of the sagittal section is an important step in the study of the relation between vocal tract geometry and speech acoustics. We present a new model to perform this transformation, inspired by the alpha beta model of Heinz & Stevens (1965). Our model is based on analysis of a vocal tract cast for large sagittal dimensions and for small sagittal dimensions on CT scans of the vocal tract constriction zones for the three cardinal vowels [i, a, u] of French. We extracted two sets of coefficients, appropriate for large and small sagittal dimensions respectively. We then compared the predictions of the model with those of other models from the literature. Finally, the usefulness of this dual coefficient procedure for the acoustic simulation of vowels was tested using sagittal sections generated by an acoustic model of the vocal tract.

The acoustic sensitivity of vocal tract constrictions: a preliminary report

A basic premise underlying most recent vocal tract modeling is that the area functions at and near vocal tract constrictions are the ones most critical to the acoustic output; it is also the central point of many hypotheses concerning speech production, that speech targets are coded neurophysiologically with respect to acoustically significant area function features. To determine the relationship between constriction parameters and the acoustic output, we performed a number of vocal tract simulations that perturbed the locations and cross-sectional areas of the points of constriction for the three cardinal vowels, [i], [a] and [u]. The vocal tract area functions of the steady state vowels were approximated by first obtaining midsagittal X-rays of a single speaker’s production of the three vowels. These approximations were then used to construct a set of articulatory-derived acoustic continua that represented systematic perturbations of the cross-dimensions and locations of the constrictions for each sound. Empirically derived coefficients were used to convert the measured cross-dimensions to area functions. A third program calculated the transfer function and formants for each sample. Results of the perturbation analysis showed that formants for each of the vowels were relatively sensitive to minimal changes in crosssectional area but relatively insensitive to larger changes in constriction location. Vowel perception, however, was highly resistant to these step changes, suggesting a many-to-one relationship between articulatory/acoustic and perceptual targets.

Articulatory dynamics of deaf speakers during plosive production: Aerodynamic and kinematic evidence

The production of speech requires precise movement and timing of the articulators to accurately valve the egressive airstream. While evident that deaf speakers often experience difficulty controlling such valves for speech production, the nature of such valving difficulties remains elusive. Previous aerodynamic studies have been primarily descriptive, characterizing steady-state aspects of speech production. The present study described and compared dynamic aspects of deaf and normal-hearing speakers' speech production using aerodynamic and kinematic measures. Five profoundly deaf and two normal-hearing young adults produced multiple tokens of voiced and voiceless plosive segments in varied vowel contexts, while simultaneous measures were obtained of oral and nasal airflow, oral pressure, and electroglottograph and acoustic signals. Conductance of oral and nasal vocal tract constrictions were used to describe and compare the magnitude and relative timing of articulatory gestures for deaf and hearing subjects. Computer simulation of the supraglottal air pressure and airflow waveforms was used to further investigate how these waveform variations may be related to articulatory maneuvers. Implications for speech training will be discussed. [Research supported by the Whitaker Foundation.]

Singing synthesis with models of phonatory and articulatory kinematics

Singing synthesis to date has been attempted primarily in the acoustic domain. In an effort to learn more about the interactions between the source and subglottal and supraglottal resonators, a simulation strategy is employed that computes pressures and flows on the basis of vocal fold and articulatory movement. Some aspects of the perception of vocal registers are shown to be related to subglottal resonances. In particular, the first subglottal formant (ca. 500 Hz) helps to trigger the involuntary chest‐falsetto transition in untrained voices. Roundness in the medial surface contour of the vocal folds also helps to distinguish chest‐falsetto and male‐female differences. Vocal tract constrictions in the vicinity of the glottis are shown to affect vocal quality, in particular, the perception of vocal ring. Frication in the glottis and the vocal tract is computed on the basis of critical Reynolds numbers and is an automatic consequence of changes in subglottal pressure and airway constriction. Some examples...

Laryngeal compensation following sudden oral perturbation

Recently, there have been a number of demonstrations of rapid goal‐directed compensation in remote articulators when an articulator is perturbed unexpectedly during ongoing speech. Much of this research, however, has involved articulators that cooperate to produce a single vocal tract constriction (i.e., tongue‐jaw, lips‐jaw). In this experiment, spatially more separate articulators are examined that are simultaneously active in the production of a phonetic segment (i.e., the larynx and the lip‐jaw complex). Three subjects produced the nonsense utterance “/ipip/ again” and the lower lip was unexpectedly loaded in the first vowel or during the closure for the first /p/ on a small proportion of the trials. Laryngeal behavior was monitored using transillumination and fiberoptic videotaping. In addition, intraoral air pressure just above the folds was monitored. Oral movements were recorded with a Selspot system. Acoustically, the first /p/ closure in “ipip” was shorter in duration and the voice onset times were longer in the perturbed trials. An examination of the laryngeal gestures during the production of the first /p/ revealed longer adduction durations in the perturbed conditions than in the control trials and a longer overall abduction/adduction cycle. The results will be discussed in terms of task‐dependent articulatory coupling. [Work supported by NINCDS.]

Effects of a vocal-tract constriction on the glottal source: experimental and modelling studies

The effects of a vocal-tract constriction on the glottal source were examined, based on acoustic and electroglottographic (EGG) data. Six subjects phonated through an apparatus in which constrictions of various sizes were alternated with a relatively unconstricted configuration. Measurements of glottal open time were made from the EGG data, and the effect of the constriction on glottal pulse shape was inferred from the spectrum of the acoustic signal. The data show a longer open time for the more constricted configurations, as well as a decreased pulse area, less abrupt closing slope of the pulse, and wider bandwidth of the first formant. Variability in all of the measures was apparent across subjects. We also examined the behavior of a two-mass model of the vocal folds which it is coupled to vocal-tract configurations with various degrees of constriction. There was general agreement between the glottal pulse waveforms generated by the model and those inferred from the speech experiments.

Articulatory coordination and the clinical profile of two cleft palate speakers

Articulatory movements of two post surgical cleft palate patients were studied using cinefluorographic procedures (24 frames per second). The subjects both achieved closure during a sustained production of /u/ but had different clinical profiles. The coordination of the velum with other articulators (jaw, tongue dorsum and tongue tip) and with voicing was analysed in order to demonstrate the hypothesized relationship between articulatory timing and nasality. The results show that the movement of velum differed dramatically between these two subjects. For S2, the subject with the higher nasality ratings, velar closure was achieved less consistently than for S1. When it was achieved it often came after voice onset or after the maximum vocal tract constriction had occurred. These relationships, it is argued, are conducive to increases in nasal resonance. The data suggest that many of the timing patterns shown may be accounted for by the mechanical constraints placed on the velum by the lowering of the jaw and tongue. It is suggested that in order to determine precise role of neuromuscular and mechanical parameters in velar function or dysfunction, comprehensive modelling of velar activity needs to be pursued.

Intelligibility alterations in an oral cancer patient following primary surgery and two reconstructions: A case study

Intelligibility and perceptual characteristics were examined in a bilingual Zulu/Xhosa-speaking patient following glossectomy and mandibulectomy with primary closure and two subsequent reconstruction using osteomyocutaneous flaps. Changes across a twelve-month period were investigated, using intelligibility tests administered to native speakers, lateral view xeroradiography and fiberoptic investigations. Findings emphasise the need for reconstructive surgery to strive for preservation of articulator mobility, relationships between articulators and the positioning of vocal tract constrictions. The possibility of atrophic changes deleterious to speech and a more influential role for the speech therapist are discussed.

Attempts by human speakers to reproduce Fant's nomograms

Fant's nomograms, which constitute a simulation of the acoustic resonances which result from different vocal tract shapes, were checked against natural vowels by two phoneticians carefully producing a full range of vowel articulation in which (a) the location of the minimum aperture in the vocal tract and (b) the lip aperture were separately varied. Spectrographic measurements of formant frequencies were made, some with synchronised lip photographs. Ultrasonic and radiographic methods were used to verify vocal tract constriction size. In many major respects our data agreed with Fant's predictions, but three main kinds of discrepancies were noted: firstly, we could not produce as great a range of variations as occurs in the nomograms; secondly, when an [i]-like constriction is moved as far forward as possible, the frequency of F2 does not decrease; and thirdly, variations in lip rounding affect high front vowels and high back vowels differently with no gradual change from one class to the other as in Fant's data.

On the dissociation of spectral and temporal cues to the voicing distinction in initial stop consonants.

It has been claimed that a rising first-formant (F1) transition is an important cue to the voiced–voiceless distinction for syllable-initial, prestressed stop consonants in English. Lisker [J. Acoust. Soc. Am. 57, 1547–1551 (L) (1975)] has pointed out that the acoustic manipulations suggesting a role for F1 have involved covariation of the onset frequency of F1 with the duration, and hence the frequency extent, of the F1 transition; he has argued that effects hitherto ascribed to the transition are more properly attributed to its onset. Two experiments are reported in which F1 onset frequency and F1 transition duration/extent were manipulated independently. The results confirm Lisker’s suggestion that the major effect of F1 in initial voicing contrasts is determined by its perceived frequency at the onset of voicing and show that a periodically excited F1 transition is not, per se, a positive cue to voicing. In further experiments, the relative levels and the frequencies at the onset of voicing of both F1 and F2 were manipulated. The influences on the perception of stop-consonant voicing that resulted were determined specifically by the frequency of F1 and not by its absolute or relative level or by the overall distribution of energy in the spectrum. The results demonstrate a complementary relationship between perceptual cue sensitivity and production constraints: In production, the VOT characterizing a particular stop consonant varies inversely with the degree of vocal-tract constriction, and hence with the frequency of F1, required by the phoneme following the stop; in perception, the lower the frequency of F1 at the onset of voicing, the longer the VOT that is required to cue voicelessness. In this way, the inclusion of F1 onset frequency in the cue repertoire for voicing, and the establishment of the cue trading relationship, reduce the problem of contextual variation that would be met were VOT alone, or some other amalgam of cues, the only basis of the voicing distinction.

The Motor Organization of Some Speech Gestures

EMG recordings from several muscles controlling tongue body movement for various VCV and VCCV utterances were examined to uncover the factors influencing the extent and direction of the coarticulatory reorganization of motor commands for speech gestures, and to reveal physiological correlates of syllable boundaries. The primary determiner of the direction of the reorganization appears to be the individual muscle's function in increasing or decreasing vocal tract constriction (closure and release). Muscles producing greater constrictions show anticipatory coarticulation while those producing greater openings show postcipatory coarticulation. Since consonants are produced with greater vocal tract constriction than are vowels, they limit the extent and direction of coarticulation. Thus, reorganization at the motor command level is shown for both anticipatory and postcipatory coarticulation. Syllabic units appear as VC sequences for muscles constricting the vocal tract and CV sequences for muscles expanding the vocal tract. [Supported by NIDR Grant DE01774.]

A Cinefluorographic Study of the Emphatic-Nonemphatic Feature in Arabic as a Correlate of the English Tense-Lax Feature

Previous investigations [Klatt and Stevens, “Pharyngeal Consonants,” QPR 93, 207–216 (1969)] show that there are well-defined places of articulation with distinctive acoustic properties which take place when the vocal tract constriction is made within the regions between the velum and the glottis. These sounds are traditionally known as emphatic and are found in the Semitic languages, in particular, Arabic. The high-speed cinefluorographic films made of three native speakers of Arabic answer several questions concerning the fine details of physiological activities which involve the tongue root with respect to the velum and the interior pharyngeal wall during articulating certain sounds, namely the emphatic and their nonemphatic counterparts in Arabic. The study also investigates the timing differences for other major articulator movements which serve to differentiate classes of sounds. [This project was supported, in part, by a Public Health Service research grant, the National Institute of Dental Research.]

Fundamental-Frequency Measures and Ratings of the Speech of Patients with Cancer of the Vocal Folds

Speech samples of five patients with laryngeal cancer involving the vocal folds and five matched normal speakers were analyzed with respect to: (1) distribution of fundamental frequency; (2) perturbations in successive glottal periods; (3) maximum rate of change of fundamental frequency; and (4) perturbations in fundamental frequency occurring during the production of specific consonants (vocal-tract constrictions). The pathological speakers exhibited a more restricted distribution of fundamental frequency than the normal speakers. However, the other measures did not appear to differentiate the two groups of speakers. The results of listening tests, in which the same speech samples were rated with respect to hoarseness, harshness, and breathiness, are also discussed.