Search

This letter shows the application of backward differentiation formulas to solve a differential equation by Rothenberg [(1981). Department for Speech, Music and Hearing Quarterly Progress and Status Report (KTH Royal Institute of Technology, Stockholm, Sweden), Vol. 22], which models the glottal airflow rate vs the glottal area. The formulas avoid a singularity of the equation that occurs when the glottal area is zero and that prevents the application of Runge-Kutta and other numerical methods. They can also be used when the equation is augmented with a glottal air viscosity term to eliminate non-differentiability at glottal opening and closure.

This letter introduces a parametrization of the vocal tract area function based on the position of a few points along the vocal tract. A QR decomposition algorithm is applied to area function data in various vowel configurations in order to identify those points with the most independent position patterns across vowels. Each point defines the shape of an associated kinematic region, and the overall area function is determined by the combination of the kinematic regions' shapes. The results show that only four data points, located at the tongue body, lips, and two at the tongue back, are enough to obtain accurate reconstructions of the vowels' area functions.

This letter proposes a correction to an equation by Titze [J. Acoust. Soc. Am. 75, 570-580 (1984)] for the volume velocity of the glottal air flow given the glottal area and other laryngeal parameters. It shows that the equation produces non-differentiable waveforms at the instants of glottal closure and opening, if the glottal area is also not differentiable at those instants. By adding an air viscosity term to the equation, twice-differentiability is obtained. Also, the letter corrects a sign error in the original formulation.

This article presents an analysis of entrained oscillations of the right and left vocal folds in the presence of asymmetries. A simple one-mass model is proposed for each vocal fold. A stiffness asymmetry and open glottis oscillations are considered first, and regions of oscillation are determined by a stability analysis and an averaging technique. The results show that the subglottal threshold pressure for 1:1 entrainment increases with the asymmetry. Within that region, both folds oscillate with the same amplitude and with the lax fold delayed in time with regard to the tense fold. At large asymmetries, a region involving several different phase entrainments or toroidal regimes at constant threshold pressure appears. The effect of vocal fold collisions and asymmetry in the damping coefficients of the oscillators are explored next by means of numerical analyses. It is shown that the damping asymmetry expands the 1:1 entrainment region at low subglottal pressures across the whole asymmetry range. In the expanded region, the oscillator with the lowest natural frequency is dominant and the other oscillator has a large phase advance and small amplitude. The theoretical results are finally compared with data collected from a mechanical replica of the vocal folds.

Phonation models commonly rely on the assumption of a two-dimensional glottal geometry to assess kinetic and viscous flow losses. In this paper, the glottal cross-section shape is taken into account in the flow model in order to capture its influence on vocal folds oscillation. For the assessed cross-section shapes (rectangular, elliptical, or circular segment) the minimum pressure threshold enabling to sustain vocal folds oscillation is altered for constriction degrees smaller than 75%. The discrepancy between cross-section shapes increases as the constriction degree decreases.

International audience; This paper analyzes the interaction between the vocal folds and vocal tract at phonation onset due to the acoustical coupling between both systems. Data collected from a mechanical replica of the vocal folds show that changes in vocal tract length induce fluctuations in the oscillation threshold values of both subglottal pressure and frequency. Frequency jumps and maxima of the threshold pressure occur when the oscillation frequency is slightly above a vocal tract resonance. Both the downstream and upstream vocal tracts may produce those same effects. A simple mathematical model is next proposed, based on a lumped description of tissue mechanics, quasi-steady flow and one-dimensional acoustics. The model shows that the frequency jumps are produced by saddle-node bifurcations between limit cycles forming a classical pattern of a cusp catastrophe. The transition from a low frequency oscillation to a high frequency one may be achieved through two different paths: in case of a large acoustical coupling (narrow vocal tract) or high subglottal pressure, the bifurcations are crossed, which causes a frequency jump with a hysteresis loop. By reducing the acoustical coupling (wide vocal tract) or the subglottal pressure, a path around the bifurcations may be followed with a smooth frequency variation.

Previous authors have established that stop consonant voicing is more limited in young children than adults, and have ascribed this to immature vocal-tract pressure management. Physical development relevant to speech aerodynamics continues into adolescence, suggesting that consonant voicing development may also persist into the school-age years. This study explored the relationship between stop consonant voicing and intraoral pressure contours in women, 5 year olds, and 10 year olds. Productions of intervocalic /p b/ were recorded from eight speakers at each age. Measures were made of stop consonant voicing and delta, a measure designed to characterize the time course of intraoral pressure increase in stops, following Muller and Brown [Speech and Language: Advances in Basic Research and Practice, edited by N. Lass (Academic, Madison, 1980), Vol. 4, pp. 318-389]. Age effects for stop consonant voicing and delta were not statistically significant, but correlations between delta and stop voicing were less often significant and sometimes reversed in the children, providing some evidence of immature aerodynamic control. The current data, as well as those of Muller and Brown, also show that the delta measure may yield some paradoxical values, indicating that more work is needed on methods of assessing time-varying characteristics of intraoral pressure.

This letter analyzes the oscillation onset-offset conditions of the vocal folds as a function of laryngeal size. A version of the two-mass model of the vocal folds is used, coupled to a two-tube approximation of the vocal tract in configuration for the vowel /a/. The standard male configurations of the laryngeal and vocal tract models are used as reference, and their dimensions are scaled using a single factor. Simulations of the vocal fold oscillation and oral output are produced for varying values of the scaling factor. The results show that the oscillation threshold conditions become more restricted for smaller laryngeal sizes, such as those appropriate for females and children.

In this study we use a low-dimensional laryngeal model to reproduce temporal variations in oral airflow produced by speakers in the vicinity of an abduction gesture. It attempts to characterize these temporal patterns in terms of biomechanical parameters such as glottal area, vocal fold stiffness, subglottal pressure, and gender differences in laryngeal dimensions. A two-mass model of the vocal folds coupled to a two-tube approximation of the vocal tract is fitted to oral airflow records measured in men and women during the production of /aha/ utterances, using the subglottal pressure, glottal width, and Q factor as control parameters. The results show that the model is capable of reproducing the airflow records with good approximation. A nonlinear damping characteristics is needed, to reproduce the flow variation at glottal abduction. Devoicing is achieved by the combined action of vocal fold abduction, the decrease of subglottal pressure, and the increase of vocal fold tension. In general, the female larynx has a more restricted region of vocal fold oscillation than the male one. This would explain the more frequent devoicing in glottal abduction-adduction gestures for /h/ in running speech by women, compared to men.

The dynamics of the two‐mass model of the vocal fold oscillation is analyzed. It is shown that the oscillation may occur around two equilibrium positions, and that each case presents similar features as the chest and falsetto registers, suggesting a relation between them. The switch between equilibrium positions is caused by a transcritical bifurcation phenomenon.

In previous experimental studies it has been observed that the minimum lung pressure to sustain vocal fold oscillation after its onset is lower than the threshold pressure needed to initiate it. This phenomenon is studied analytically using a previous body-cover model of the vocal folds and applying the describing function method to the general case of large amplitude oscillations. It is shown that the phenomenon is a consequence of the nonlinear characteristic of the effective aerodynamic damping introduced by the air pressure acting on the vocal folds. The results predict a value for minimum sustaining pressure equal to half the threshold pressure for a rectangular prephonatory glottis, which is in the order of experimental results.

In obstruent consonants, a major constriction in the upper vocal tract yields an increase in intraoral pressure (Pio). Phonation requires that subglottal pressure (Psub) exceed Pio by a threshold value, so as the transglottal pressure reaches the threshold, phonation will cease. This work investigates how Pio levels at phonation offset and onset vary before and after different German voiceless obstruents (stop, fricative, affricates, clusters), and with following high vs low vowels. Articulatory contacts, measured using electropalatography, were recorded simultaneously with Pio to clarify how supraglottal constrictions affect Pio. Effects of consonant type on phonation thresholds could be explained mainly in terms of the magnitude and timing of vocal-fold abduction. Phonation offset occurred at lower values of Pio before fricative-initial sequences than stop-initial sequences, and onset occurred at higher levels of Pio following the unaspirated stops of clusters compared to fricatives, affricates, and aspirated stops. The vowel effects were somewhat surprising: High vowels had an inhibitory effect at voicing offset (phonation ceasing at lower values of Pio) in short-duration consonant sequences, but a facilitating effect on phonation onset that was consistent across consonantal contexts. The vowel influences appear to reflect a combination of vocal-fold characteristics and vocal-tract impedance.In obstruent consonants, a major constriction in the upper vocal tract yields an increase in intraoral pressure (Pio). Phonation requires that subglottal pressure (Psub) exceed Pio by a threshold value, so as the transglottal pressure reaches the threshold, phonation will cease. This work investigates how Pio levels at phonation offset and onset vary before and after different German voiceless obstruents (stop, fricative, affricates, clusters), and with following high vs low vowels. Articulatory contacts, measured using electropalatography, were recorded simultaneously with Pio to clarify how supraglottal constrictions affect Pio. Effects of consonant type on phonation thresholds could be explained mainly in terms of the magnitude and timing of vocal-fold abduction. Phonation offset occurred at lower values of Pio before fricative-initial sequences than stop-initial sequences, and onset occurred at higher levels of Pio following the unaspirated stops of clusters compared to fricatives, affricates, and asp...

The dynamics of the large‐amplitude oscillation of the vocal folds is analyzed using the two‐mass model. First, the equilibrium positions are determined in the case of a rectangular prephonatory glottis, and the existence of two equilibrium positions besides the rest position is shown. Their stability is examined and a bifurcation diagram is derived with a normalized subglottal pressure and a coupling coefficient as control parameters. Phase plane plots are shown to illustrate the results. The cases of convergent and divergent prephonatory glottis are then briefly considered. The main results are finally discussed relative to previous analytical works; it is shown that they disprove the previous oscillation theory based on the existence of a glottal negative differential resistance.

This Letter presents an extension of a previous equation for the phonation threshold pressure by Titze [I. R. Titze, J. Acoust. Soc. Am. 83, 1536–1552 (1988)]. The extended equation contains the vocal-fold oscillation frequency as an explicit factor. It is derived from the mucosal wave model of the vocal folds by considering the general case of an arbitrary time delay for the mucosal wave to travel the glottal height. The results are illustrated with a numerical example, which shows good qualitative agreement with experimental measures.

Vocal learning is a complex trait that is expressed differently across different taxa. While many of the best-studied species exhibit close-ended learning, in which vocal signals are learned from adult tutors during juvenile critical learning periods, other species have open-ended learning in which new signals are learned throughout life. Budgerigars (Melopsittacus undulatus) are an extreme example of an open-ended learner, in which both sexes have a repertoire of multiple contact calls types that continually change through adulthood to match the call types of social associates. We discuss the analytical challenges posed by the rapid plasticity of the budgerigar vocal repertoire and compare results from several different approaches to characterizing call variation. We then consider the social implications and benefits of contact call matching in fission–fusion groups. Finally, we examine the mechanisms underlying this plasticity, with a special focus on the role of the gene FoxP2. We find downregulation of FoxP2 mRNA and protein in the primary parrot vocal learning center, MMSt, across a variety of social conditions in which birds also show vocal plasticity. The results support the hypothesis that FoxP2 is a key gene regulating the neural plasticity that underlies the persistent vocal plasticity exhibited by budgerigars.

This study investigates cross-speaker differences in the factors that predict voicing thresholds during abduction–adduction gestures in six normal women. Measures of baseline airflow, pulse amplitude, subglottal pressure, and fundamental frequency were made at voicing offset and onset during intervocalic /h/, produced in varying vowel environments and at different loudness levels, and subjected to relational analyses to determine which factors were most strongly related to the timing of voicing cessation or initiation. The data indicate that (a) all speakers showed differences between voicing offsets and onsets, but the degree of this effect varied across speakers; (b) loudness and vowel environment have speaker-specific effects on the likelihood of devoicing during /h/; and (c) baseline flow measures significantly predicted times of voicing offset and onset in all participants, but other variables contributing to voice timing differed across speakers. Overall, the results suggest that individual speakers have unique methods of achieving phonatory goals during running speech. These data contribute to the literature on individual differences in laryngeal function, and serve as a means of evaluating how well laryngeal models can reproduce the range of voicing behavior used by speakers during running speech tasks.

In this paper we present an algorithm for building an empirical model of facial biomechanics from a set of displacement records of markers located on the face of a subject producing speech. Markers are grouped into clusters, which have a unique primary marker and a number of secondary markers with an associated weight. Motion of the secondary markers is computed as the weighted sum of the primary markers of the clusters to which they belong. This model may be used to produce facial animations, by driving the primary markers with measured kinematic signals.

The harmonics-to-noise ratio (HNR) has been used to quantify the waveform irregularity of voice signals [Yumoto et al., J. Acoust. Soc. Am. 71, 1544-1550 (1982)]. This measure assumes that the signal consists of two components: a harmonic component, which is the common pattern that repeats from cycle-to-cycle, and an additive noise component, which produces the cycle-to-cycle irregularity. It has been shown [J. Qi, J. Acoust. Soc. Am. 92, 2569-2576 (1992)] that a valid computation of the HNR requires a nonlinear time normalization of the cycle wavelets to remove phase differences between them. This paper shows the application of functional data analysis to perform an optimal nonlinear normalization and compute the HNR of voice signals. Results obtained for the same signals using zero-padding, linear normalization, and dynamic programming algorithms are presented for comparison. Functional data analysis offers certain advantages over other approaches: it preserves meaningful features of signal shape, produces differentiable results, and allows flexibility in selecting the optimization criteria for the wavelet alignment. An extension of the technique for the time normalization of simultaneous voice signals (such as acoustic, EGG, and airflow signals) is also shown. The general purpose of this article is to illustrate the potential of functional data analysis as a powerful analytical tool for studying aspects of the voice production process.

Modeling the peripheral speech motor system can advance the understanding of speech motor control and audiovisual speech perception. A 3-D physical model of the human face is presented. The model represents the soft tissue biomechanics with a multilayer deformable mesh. The mesh is controlled by a set of modeled facial muscles which uses a standard Hill-type representation of muscle dynamics. In a test of the model, recorded intramuscular electromyography (EMG) was used to activate the modeled muscles and the kinematics of the mesh was compared with 3-D kinematics recorded with OPTOTRAK. Overall, there was a good match between the recorded data and the model's movements. Animations of the model are provided as MPEG movies.

This paper presents a theoretical study on the differences in the biomechanical parameters of the vocal folds between oscillation onset and offset. The dynamics of the oscillation is analyzed from the perspective of the theory of nonlinear dynamical systems, using a mucosal wave model of the vocal folds with the subglottal pressure and the vocal fold half-width as control parameters. It is shown that the oscillation onset occurs through a Hopf bifurcation of the subcritical type, at which an unstable limit cycle is generated. Also, the oscillation offset occurs at a cyclic fold bifurcation, at which the unstable limit cycle and a stable limit cycle (the actual vocal fold oscillation) coalesce and cancel each other. Both bifurcations combine to form an “oscillation hysteresis” phenomenon, common in cases of flow-induced oscillations. An analytical expression for the onset/offset ratio of parameters is derived. The onset/offset ratio is in the range of 0.5–1, in agreement with the experimental evidence. This value depends on the phase delay in motion of the upper edge of the vocal folds versus the lower edge, and on the particular model adopted for airflow separation within the glottis.

Recent experimental measurements have shown a nonlinear relation between the phonation threshold pressure and the prephonatory glottal width, with a minimum for the threshold pressure which would indicate the existence of an optimal glottal width for ease of phonation [I. R. Titze et al., J. Acoust. Soc. Am. 97, 3080–3084 (1995)]. This relation is studied analytically using a simplified vocal fold model which includes an explicit term for the air pressure losses due to glottal viscous resistance. It is shown that the observed nonlinearity may be a consequence of the viscous pressure losses, which cause an increase of the threshold pressure at small values of the prephonatory glottal width.

The dynamical principles of the vocal fold oscillation at phonation were set forth by Titze (I. R. Titze, J. Acoust. Soc. Am. 83, 1536‐1552 , 1988), by representing motion of the tissues as a surface wave propagating in the direction of the airflow. An important result of his work was an equation for the phonation threshold value of lung pressure, defined as the minimum value required to initiate the vocal fold oscillation. Titze's model assumed a small time delay for the mucosal wave to travel along the vocal folds, with the consequence that the phonation threshold pressure results independent of the oscillation frequency. Here, we consider an extension of his model for an arbitrary time delay. Our results show that the threshold pressure increases with oscillation frequency following a x/sin(x) law. We investigate the validity of the theoretical equation by comparing it with pressure measures from a mechanical replica of the vocal folds, under various configurations. In general, the equation shows good ...

To maintain voicing during a stop consonant, adult speakers typically perform articulatory actions that increase supraglottal volumes and slow the rate at which of intraoral pressure (Pio) rises. In an influential study, Muller and Brown [in Speech and Language: Advances in Basic Research and Practice 4, edited by N. Lass (Academic, New York, 1980), pp. 318–389] proposed a quantitative measure of Pio pulse shape, based on the difference between (a) the slope from pressure at closure to average pressure and (b) from average pressure to pressure at release. We recently applied these techniques to data from women and child speakers of English and observed some shortcomings in Muller and Brown’s measurement technique, such that the slope difference angle did not clearly reflect the actual pressure pulse shape. The purpose of this paper is to explore new methods of analyzing intraoral pressure contours, based on fitting a mathematical model to the pressure pulse shapes. It will report our progress and compare our results with the previous technique.

A dynamical, muscle‐based model of the face is being developed to extend the facial model of Terzopoulos et al. [e.g., D. Terzopoulos and K. Waters, IEEE Trans. Pattern Anal. Machine Intell. 15, 569–579 (1993)]. The purpose of this work is to characterize facial dynamics during speech with a physiologically realistic model. The model consists of a multilayered deformable mesh of lumped masses connected by springs and viscous elements which represents the layered structure of facial tissue. The spring and viscous constants approximate the stress/strain and viscous characteristics of facial skin. The mesh is deformed by forces generated by a set of modeled muscles of facial expression whose physical characteristics are being determined empirically. The shape of the facial model is individualized to subjects facial morphology with data from a laser ranger finder (Cyberware scanner). In this report, work on driving the model with intramuscular, perioral EMG signals is presented. Recordings of the sampled thre...