Velum Movement Research Articles

Vowel height and velum position in German: Insights from a real-time magnetic resonance imaging study.

Velum position was analysed as a function of vowel height in German tense and lax vowels preceding a nasal or oral consonant. Findings from previous research suggest an interdependence between vowel height and the degree of velum lowering, with a higher velum during high vowels and a more lowered velum during low vowels. In the current study, data were presented from 33 native speakers of Standard German who were measured via non-invasive high quality real-time magnetic resonance imaging. The focus was on exploring the spatiotemporal extent of velum lowering in tense and lax /a, i, o, ø/, which was done by analysing velum movement trajectories over the course of VN and VC sequences in CVNV and CVCV sequences by means of functional principal component analysis. Analyses focused on the impact of the vowel category and vowel tenseness. Data indicated that not only the position of the velum was affected by these factors but also the timing of velum closure. Moreover, it is argued that the effect of vowel height was to be better interpreted in terms of the physiological constriction location of vowels, i.e., the specific tongue position rather than phonetic vowel height.

Speed of velum movement during nasal segments and rest intervals: A cineradiographic study of French and English speech

While opening/closing of the velopharyngeal port (VPP) in speech has been much studied, the speed of these movements has been largely overlooked. The present study compares opening/closing velocities of the VPP in French and English, testing relation to distance traveled and speech-related versus physiological movements. Running speech samples from nine Quebecois French speakers and four Canadian English speakers were obtained from the Université Laval X-ray videofluorography database [Munhall et al., J. Acoust. Soc. Am., 98(2), 1222–1224 (1995)]. Using ImageJ software, we tracked VPP opening/closing movements during two types of events: phonologically nasal segments and rest intervals between chunks of speech. We calculated velocity of VPP opening/closing during these events and analyzed the data using linear mixed-effects models to identify differences between the nasals and rest intervals as well as for any cross-linguistic differences. Results indicated that: (1) VPP closure was faster following English nasals than French nasals; (2) VPP opening was faster than closure for rest intervals in French; and (3) VPP opening/closing speeds were faster coming into/out of rest position than into/out of nasals in French. Preliminary cross-language observations support a correspondence between velocity and distance. [Work supported by NIH and NSERC.]

Planting the seed for sound change: Evidence from real-time MRI of velum kinematics in German

Velum movement signals generated from real-time magnetic resonance imaging videos of thirty-five German speakers were used to investigate the physiological conditions that might promote sound change involving the development of contrastive vowel nasality. The results suggest that, in comparison to when a nasal consonant precedes a voiced obstruent, the velum gesture associated with a nasal consonant preceding a voiceless obstruent undergoes gestural rescaling and temporal rephasing. This further suggests that the diachronic development of contrastive vowel nasality comprises two stages: the first stage involves gestural shortening and realignment, while the second stage involves a trading relationship between source and effect.

X-ray analysis of velum movement in continuous speech

In speech, the velopharyngeal port (VPP) is closed for oral sounds and open for nasal consonants and nasalized vowels. While VPP opening has been much studied, the stimuli have typically been sustained vowels or short CVC words. To study velum movement in continuous speech, we examined X-ray film database data [Munhall et al., J. Acoust Soc. Am. 98(2), 1222–1224 (1995)] from French and English speakers. The films' speech audio were annotated and velum movement in each frame was tracked using videokymography in ImageJ. Degree of VPP opening was normalized by speaker and plotted in arbitrary units (au). Each velum opening and closure excursion created a peak (max value 1.0) with a corresponding opening and closing slope. Preliminary analysis of two English and six French speakers shows the average VPP opening was greatest during inter-utterance pauses at 0.54 au (SD 0.24), while for nasals the opening was 0.34 (SD 0.17) and for oral sounds the velum was generally closed. There was greater mean opening for utterance-final nasals [0.41 SD(0.21)] than utterance-initial [0.25 SD(0.13)] or mid-utterance [0.32 SD(0.15)] nasals. Across-speaker slope analysis suggests the velum moves at a similar speed for opening and closing movements. Across-language comparison will be reported.

Assessment of velopharyngeal function with dual-planar high-resolution real-time spiral dynamic MRI.

To develop a real-time dynamic MRI method for comprehensive evaluation of velum movement during speech. Dynamic MRI has been used to study velopharyngeal insufficiency (VPI) by imaging the movement of the velum during speech, because it can provide good anatomic details with no exposed radiation. To be able to comprehensively evaluate dynamic velum movement, a real-time spiral non-balanced SSFP sequence was developed with simultaneous dual-planar coverage and improved spatial and temporal resolution using a combination of parallel imaging and spatial and temporal compressed sensing to achieve 6 × acceleration. New off-resonance correction and post-processing methods were also developed to reduce blurring and slice crosstalk. The method demonstrated good image quality for visualizing dynamic velum movement with reduced blurring and improved image homogeneity. Spatial resolution of 1.2*1.2 mm2 with 150 mm FOV and temporal resolution of 20 frames-per-second with simultaneous dual-planar coverage was achieved. This work describes a new technique for studying speech disorders using dual-planar accelerated spiral dynamic MRI.

Swallowing evaluation after surgery for obstructive sleep apnea syndrome: uvulopalatopharyngoplasty vs. expansion pharyngoplasty.

To evaluate the effect of pharyngeal surgery on swallowing pattern in patients with obstructive sleep apnea syndrome (OSAS), and to compare two surgical techniques: uvulopalatopharyngoplasty (UPPP) and expansion pharyngoplasty (EP), through videofluoroscopy. Longitudinal prospective cohort, in a tertiary referral center. 17 adult patients were enrolled this study, divided into two groups: patients who underwent UPPP (n = 10) or EP (n = 7). Swallowing videofluoroscopy (for both liquid and pasty consistences) was assessed at three different periods: before surgery, and at 14 and 28days following surgery. Comparisons were performed between pre- and post-operative (PO) swallowing conditions in the same patient, and between surgical techniques. Asymptomatic OSAS patients already presented altered swallowing pattern before surgery. Both surgical procedures led to an increased hyoid movement time and an increased frequency of laryngeal penetration in early PO during liquid ingestion. For pasty consistency, both techniques reduced velum movement time and increased pharyngeal transit time and the rate of stasis in hypopharynx. All these parameters reached or tended to reach the pre-operative indices at day PO 28. OSAS patients show sub-clinical changes in swallowing pattern before surgery. Both surgical techniques are related to transitory changes in swallowing biomechanics. Complete or partial reversal to pre-operative swallowing parameters occurs 1month after both surgery techniques.

Predicting velum movement from acoustic features—A regression approach

Although acoustical methods have been widely used in the nasality literature, a direct link between the acoustical measurements and velum movement during speech production is yet to be established. In this study, we propose a model through which the vertical movements of the velum are inferred from an acoustic feature set. An X-ray Microbeam data set collected at University of Tokyo are used for the modeling. The data recorded the vertical movements of the velum of 11 American English speakers saying both isolated words and sentences. Velum positions are recorded from tracing a metal pallet placed on top of the velum. 40 MFCC (Mel-frequency Cepstral Coefficient) features are extracted from the accompanying acoustic signal at each time frame. MFCCs of ten frames before the current frame, together with the current frame, consist of the feature vector for predicting the velum movement of the current frame. Elasticnet regression is used to reduce the dimensionality of the feature vector. In general, MFCCs from higher frequencies are penalized during model selection. The selected features are then fitted to a stepwise logistic model. For each individual speaker, the inferred velum movements in the validation set are a good fit to the actual observation as judged by the high accuracy in identifying locations of peaks and valleys and small deviance from the response. However, there exists large inter-speaker variation in terms of both movement pattern and model performance.

A nasograph and fibrescopic analysis of nasal diphtongs in Brazilian Portuguese

This paper examines velum movements during the production of front and back nasal diphtongs [ẽĩ], [ãõ] in Brazilian Portuguese. Velum movements were measured with a female speaker from Sao Paulo using a nasograph and fibrescopic video-recordings synchronized with acoustic recordings. The nasal diphthongs were always situated at the end of a syllable in real words containing nasal diphthongs. Contrasting oral diphthongs were also recorded for comparison. Our results show that there is a nasal appendix the end of the nasal diphthongs. This is made by a contact between the tongue dorsum and the velum. These observation are based on nasograph and fibrescopic data. They confirm previous measurements made by EMA and aerodynamic measurements with the same subject. This appendix is sometimes perceived as a short velar nasal consonant. The duration of nasal appendix is slightly different when front and back nasal diphthongs are compared. Data also show that the lowering of the Velum occurs gradually for a nasal diphthong. This can start at any time during the first part of the diphthong.

Inferring velum movements from acoustic features

Although acoustical methods have been widely used in the literature on nasality, a direct link between the acoustic features and velum movements during speech production is yet to be established. In this study, we propose a model through which the vertical movements of the velum are inferred from an acoustic feature set. An X-ray Microbeam data set collected at University of Tokyo is used for the modeling. The data recorded the vertical movements of the velum of 11 American English speakers saying both isolated words and sentences. Velum positions are traced by a metal pallet placed on top of the velum. 40 MFCC (Mel-frequency Cepstral Coefficient) features are extracted from the accompanying acoustic signal at each time frame. MFCC features of five frames to both sides of the current frame, together with the current frame, consist of the 440-dimensional feature vector for predicting the velum position of the current frame. The feature vectors are then fitted to a lasso regression model. The inferred velum...

Detecting Nasal Vowels in Speech Interfaces Based on Surface Electromyography.

Nasality is a very important characteristic of several languages, European Portuguese being one of them. This paper addresses the challenge of nasality detection in surface electromyography (EMG) based speech interfaces. We explore the existence of useful information about the velum movement and also assess if muscles deeper down in the face and neck region can be measured using surface electrodes, and the best electrode location to do so. The procedure we adopted uses Real-Time Magnetic Resonance Imaging (RT-MRI), collected from a set of speakers, providing a method to interpret EMG data. By ensuring compatible data recording conditions, and proper time alignment between the EMG and the RT-MRI data, we are able to accurately estimate the time when the velum moves and the type of movement when a nasal vowel occurs. The combination of these two sources revealed interesting and distinct characteristics in the EMG signal when a nasal vowel is uttered, which motivated a classification experiment. Overall results of this experiment provide evidence that it is possible to detect velum movement using sensors positioned below the ear, between mastoid process and the mandible, in the upper neck region. In a frame-based classification scenario, error rates as low as 32.5% for all speakers and 23.4% for the best speaker have been achieved, for nasal vowel detection. This outcome stands as an encouraging result, fostering the grounds for deeper exploration of the proposed approach as a promising route to the development of an EMG-based speech interface for languages with strong nasal characteristics.

COMPUTER AIDED ARTICULATORY TUTOR: A SCIENTIFIC STUDY

This paper describes the use of Computer Aided Articulation Tutor (CAAT) to conduct phonetic training to the hearing-impaired (HI) children with inner articulators as visual cues. This Articulatory tutor was developed by using Magnetic Resonance Imaging (MRI) and computer graphics techniques. The articulators include the movement of jaw, lips, tongue and velum. Ten hearing impaired (HI) children between the ages 4 and 7 were selected and trained for 10 hours across 4 weeks on 24 words. Intelligibility of HI children was investigated to find out their performance in speech perception and articulation. The post-training results indicated that HI children improved in articulation of speech sounds placed at different contexts. This 3D visual simulation tool helped HI children in perceiving the speech information significantly.

Influences of swallowing volume and viscosity on regulation of levator veli palatini muscle activity during swallowing

This study examined the aspect of the regulation of velum movement in the transition from the oral to pharyngeal phases of swallowing in relation to changes in the swallowing volume and viscosity by means of measurment of levator veli palatini muscle activity. The subjects were nine normal adults, ranging in age from 24 to 30 years. The swallowing volume was set at 1/4, 1/2 and 1 volume of the optimum volume of green tea for swallowing determined in each subject, and the viscosity was adjusted to 0, 2·0 and 4·6 Pa·s by mixing with thickener. Nine test foods were prepared in total. The electromyographic activity of the levator veli palatini muscle was monitored using bipolar hooked wire electrodes. The levator veli palatini muscle activity was defined as the integrated electromyographic wave. The mean in swallowing each test food was determined in each subject. The levator veli palatini muscle activity increased with the swallowing volume for all subjects (P < 0·05) and decreased inversely with the viscosity for six subjects (P < 0·05), but no change with the increase in the viscosity was noted for three subjects. This study clarified the aspect of the regulation of velar movement with regard to the involvement of the levator veli palatini muscle in swallowing activity with changes in the swallowing volume and viscosity.

Acoustic and aerodynamic characteristics of nasal diphthongs in Brazilian Portuguese

Previous studies describe acoustic and aerodynamic aspects of nasalized vowels in Brazilian Portuguese. However, there are few studies characterizing nasal diphthongs in this language. The aim of this work is to analyze acoustic and aerodynamic characteristics of nasal diphthongs of Brazilian Portuguese spoken in the city of São Paulo. We compared oral and nasal diphthongs to identify the main features of these sounds and to understand the timing of velum movements. Our data was recorded with the Portable EVA 2 workstation. The corpus of this experiment was made of ten oral and ten nasal diphthongs, with back and front glides at the end: /aw/ and /ej/; /ãw̃/ and /ẽj̃/. Words were inserted in the following sentence [i.gʊ___kadɐ iɐ] and [i.gʊ___todʊ iɐ]. The first phrase was repeated three times with six subjects and the second with three subjects. The corpus was analyzed with the Signal Explorer and Phonédit Softwares. The aerodynamic parameters analyzed were duration, peak and volume of nasal airflow. The acoustic parameters analyzed were formants patterns and FFT spectrum. Aerodynamic and acoustic data show that in nasalized diphthongs, the nasalized vowel is followed by a nasal glide and a short nasal appendix. The peak of nasal airflow at the end of the nasal diphthong is due to the fact that the oral closure, which is made for the following voiceless stop, is produced with an open velum.

Articulatory factors influencing regressive place assimilation across word boundaries in German

This EMA study examined articulatory properties of nasal–stop and stop–stop sequences across word boundaries in German. The immediate aim was to investigate whether the greater tendency of nasals as compared to stops to exhibit regressive place assimilation results from differences in tongue-tip reduction due, in turn, to acoustic–perceptual properties of nasals. In parallel with this aim, the relevance of word frequency for assimilatory processes was investigated. Analysis of data from four speakers showed greater tongue-tip reduction in high-frequency words with a nasal, indicating a combination of factors that causes tongue-tip reduction. A further route to capturing assimilatory processes is the amount of overlap between C 1 and C 2. Analysis of this was complicated precisely by the fact that particularly for the high-frequency nasals, movement reduction was sometimes so strong that no kinematic analysis could be performed. A tentative conclusion was nonetheless that overlap tended to be greater in nasal–stop than stop–stop sequences. The discussion points out that high-frequency words in German mostly end in a nasal and concludes that it is word frequency and speakers' knowledge of acoustic–perceptual properties of nasality that allows them to simplify articulation more in nasals than stops. This account presupposes that the nasality itself remains robustly present even when the lingual gesture of the nasal consonant is strongly reduced (or overlapped by the following consonant). Velum movement data available for some of the speakers and inspection of the acoustics indicated that this was indeed the case.

Timing effects of syllable structure and stress on nasals: A real-time MRI examination

The coordination of velum and oral gestures for English [n] is studied using real-time magnetic resonance imaging (MRI) movies to reconstruct vocal tract aperture functions. This technique allows for the examination of parts of the vocal tract otherwise inaccessible to dynamic imaging or movement tracking. The present experiment considers syllable onset, coda, and juncture geminate nasals and also addresses the effects of a variety of word stress patterns on segment internal coordination. We find a bimodal timing pattern in which near-synchrony of velum lowering and tongue tip raising characterizes the timing for onsets and temporal lag between the gestures is characteristic for codas, supporting and extending the findings for [m] of Krakow [(1989). The articulatory organization of syllables: A kinematic analysis of labial and velar gestures. Doctoral Dissertation, Yale University, New Haven, CT; (1993). Nonsegmental influences on velum movement patterns: Syllables, sentences, stress, and speaking rate. In M. A. Huffman, R. A. Krakow (Eds.), Nasals, nasalization and the velum (phonetics and phonology V) (pp. 87–116). New York: Academic Press]. Intervocalic word-internal nasals are found to have timing patterns that are sensitive to the local stress context, which suggests the presence of an underlying timing specification that can yield flexibly. We consider these findings in light of the gestural coupling structures described by Goldstein and colleagues [Goldstein, L., Byrd, D., & Saltzman, E. (2006). The role of vocal tract gestural action in units understanding the evolution of phonology. In M. Arbib (Ed.), Action to language via the mirror neuron system (pp. 215–249). Cambridge: Cambridge University Press; Goldstein, L., Nam, H., Saltzman, E., & Chitoran, I. (2008). Coupled oscillator planning model of speech timing and syllable structure. In Proceedings of the 8th phonetics conference of China and the international symposium on phonetic frontiers; Nam, H., Goldstein, L., & Saltzman, E. (in press). Self-organization of syllable structure: A coupled oscillator model. In Chitoran, Coupe, Marsico, & Pellegrino (Eds.), Approaches to phonological complexity].

Nasoendoscopy of velopharynx before and during diagnostic therapy.

Nasoendoscopy is an important tool for assessing velopharyngeal function. The purpose of this study was to analyze velar and pharyngeal wall movement and velopharyngeal gap during nasoendoscopic evaluation of the velopharynx before and during diagnostic therapy. Nasoendoscopic recordings of 10 children with operated cleft lip and palate were analyzed according to the International Working Group Guidelines. Ratings of movement of velum and pharyngeal walls, and size, location and shape of gaps were analyzed by 3 speech-language pathologists (SLPs). Imaging was obtained during repetitions of the syllable/pa/during a single nasoendoscopic evaluation: (a) before diagnostic therapy, and (b) after the children were instructed to impound and increase intraoral air pressure (diagnostic therapy). Once the patients impounded and directed air pressure orally, the displacement of the velum, right, left and posterior pharyngeal walls increased 40, 70, 80, and 10%, respectively. Statistical significance for displacement was found only for right and left lateral pharyngeal walls. Reduction in gap size was observed for 30% of the patients and other 40% of the gaps disappeared. Changes in gap size were found to be statistically significant between the two conditions. In nasoendoscopic assessment, the full potential of velopharyngeal displacement may not be completely elicited when the patient is asked only to repeat a speech stimulus. Optimization of information can be done with the use of diagnostic therapy's strategies to manipulate VP function. Assuring the participation of the SLP to conduct diagnostic therapy is essential for management of velopharyngeal dysfunction.

A three-dimensional articulatory model of the velum and nasopharyngeal wall based on MRI and CT data

An original three-dimensional (3D) linear articulatory model of the velum and nasopharyngeal wall has been developed from magnetic resonance imaging (MRI) and computed tomography images of a French subject sustaining a set of 46 articulations, covering his articulatory repertoire. The velum and nasopharyngeal wall are represented by generic surface triangular meshes fitted to the 3D contours extracted from MRI for each articulation. Two degrees of freedom were uncovered by principal component analysis: first, VL accounts for 83% of the velum variance, corresponding to an oblique vertical movement seemingly related to the levator veli palatini muscle; second, VS explains another 6% of the velum variance, controlling a mostly horizontal movement possibly related to the sphincter action of the superior pharyngeal constrictor. The nasopharyngeal wall is also controlled by VL for 47% of its variance. Electromagnetic articulographic data recorded on the velum fitted these parameters exactly, and may serve to recover dynamic velum 3D shapes. The main oral and nasopharyngeal area functions controlled by the articulatory model, complemented by the area functions derived from the complex geometry of each nasal passage extracted from coronal MRIs, were fed to an acoustic model and gave promising results about the influence of velum movements on the spectral characteristics of nasals.

Syllable structure effects on velum-oral coordination evaluated with real-time MRI

Seminal work by Krakow (PhD. Diss., Yale University, 1989, Phonetics and Phonology 5, 87–116, 1993) has indicated that intrasegmental coordination of articulatory gestures varies systematically as a function of syllable position. Specifically, onset and coda nasals display different lag times between the velum and oral gestural components. In onset nasals, velum lowering is achieved roughly synchronously with oral constriction, while in codas, velum lowering precedes oral constriction. However, Krakow’s study was limited by its reliance on indirect measures of velum movement. Nor did her work examine nasals other than [m] or syllable organizations other than singleton onsets and codas. Our study employs real-time magnetic resonance imaging [Narayanan et al., J. Acoust. Soc. Am. 115, 1771–1776 (2004); Mathiak et al., Int. J. of Lang. &amp; Comm. Disorders 35, 419–425 (2000)] to acquire direct information about the key vocal tract variables of velum aperture and oral constriction, thereby allowing the calculation of relative gestural timing. We investigate the effects of syllabification on interarticulatory timing in [n], and, in addition to examining codas and onsets, further consider juncture geminates spanning word boundaries. Preliminary real-time MRI results from one of three anticipated subjects do find the predicted timing difference for [n]. Further, we find that the relative timing in juncture geminates mirrors that of coda [n] but presents a velum aperture intermediate between coda and onset [n]. [Work supported by NIH.]

Towards a 3D articulatory model of velum based on MRI and CT images

This paper describes the processing of MRI and CT images needed for developing a 3D linear articulatory model of velum. The 3D surface that defines each organ constitutive of the vocal and nasal tracts is extracted from MRI and CT images recorded on a subject uttering a corpus of artificially sustained French vowels and consonants. First, the 2D contours of the organs have been manually extracted from the corresponding images, expanded into 3D contours, and aligned in a common 3D coordinate system. Then, for each organ, a generic mesh has been chosen and fitted by elastic deformation to each of the 46 3D shapes of the corpus. This has finally resulted in a set of organ surfaces sampled with the same number of 3D vertices for each articulation, which is appropriate for Principal Component Analysis or linear decomposition. The analysis of these data has uncovered two main uncorrelated articulatory degrees of freedom for the velum's movement. The associated parameters are used to control the model. We have in particular investigated the question of a possible correlation between jaw / tongue and velum's movement and have not find more correlation than the one found in the corpus.&#x0D;

Stochastic linear regression analysis of speech production data

Dynamic models in speech production have been traditionally based on linear regression analysis of articulatory data. The purpose of this work is to introduce a stochastic calculus methodology to the analysis of such data in speech production models. The issue of variability encountered in the analysis and description of articulatory movements during speech may be addressed with the implementation of a stochastic term, thus placing the variability in a controlled probabilistic framework. Upper lip, lower lip, jaw, and velum movements tracked optoelectronically at Haskins Laboratories [Kollia et al. J. Acoust. Soc. Am. 98, 1313–1327 (1995)] during production of a test utterance are described in this manner. The authors believe that this algorithm has wide applicability since it yields confidence interval rather than point value estimates for kinematic data description. [Work supported by NSF.]