Parametrization of the vocal tract area function using a subset selection approach (L).

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.

Numerical solution of Rothenberg's equation of the glottal airflow rate as a function of the glottal area using backward differentiation (L).

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.

Performance of Phonatory Deviation Diagrams in Synthesized Voice Analysis.

OBJECTIVE: To analyze the performance of a phonatory deviation diagram (PDD) in discriminating the presence and severity of voice deviation and the predominant voice quality of synthesized voices. METHOD: A speech-language pathologist performed the auditory-perceptual analysis of the synthesized voice (n = 871). The PDD distribution of voice signals was analyzed according to area, quadrant, shape, and density. RESULTS: Differences in signal distribution regarding the PDD area and quadrant were detected when differentiating the signals with and without voice deviation and with different predominant voice quality. Differences in signal distribution were found in all PDD parameters as a function of the severity of voice disorder. CONCLUSION: The PDD area and quadrant can differentiate normal voices from deviant synthesized voices. There are differences in signal distribution in PDD area and quadrant as a function of the severity of voice disorder and the predominant voice quality. However, the PDD area and quadrant do not differentiate the signals as a function of severity of voice disorder and differentiated only the breathy and rough voices from the normal and strained voices. PDD density is able to differentiate only signals with moderate and severe deviation. PDD shape shows differences between signals with different severities of voice deviation.

Smoothness of an equation for the glottal flow rate versus the glottal area.

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.

Self-entrainment of the right and left vocal fold oscillators.

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.

Influence of glottal cross-section shape on phonation onset.

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.

The Performance of the Acoustic Voice Quality Index and Acoustic Breathiness Index in Synthesized Voices.

OBJECTIVE: The aim of the present study was to investigate the performance of the Acoustic Voice Quality Index (AVQI) and the Acoustic Breathiness Index (ABI) in synthesized voice samples. METHOD: The validity of the AVQI and ABI performances was analyzed in synthesized voice samples controlling the degree of predefined deviations for overall voice quality (G-scale) and breathiness (B-scale). A range of 26 synthesized voice samples with various severity degrees in G-scale with and without prominence of breathiness for male and female voices were created. RESULTS: ABI received higher validity in the evaluation of breathiness than AVQI. Furthermore, ABI evaluated accurately breathiness degrees without considering roughness effects in voice samples and confirmed the findings of other studies with natural voices. Furthermore, ABI was more robust than AVQI in the evaluation of severe voice-disordered voice samples. Finally, AVQI represented moreover overall voice quality with an emphasis of breathiness evaluation and less roughness although roughness had a necessary component in overall voice quality evaluation. CONCLUSION: AVQI and ABI are two robust measurements in the evaluation of voice quality. However, ABI received fewer errors than AVQI in the analyses of higher abnormalities in the voice signal. Disturbances of other subtypes of abnormal overall voice quality such as roughness were not demonstrated in the results of ABI.

Trends in antimicrobial resistance of Shigella species in Peru, 2011-2020.

Objective: To describe the frequency of antimicrobial resistance rates and spatial-temporal distribution of Shigella species from the last 10 years in Peru. Methods: A cross-sectional descriptive study was carried out. A total of 1668 Shigella strains, remitted as part of the national enteric pathogen surveillance from 2011 to 2020, were analysed. The strains were confirmed by conventional tests and serotyped with polyvalent and monovalent antibodies. Also, antimicrobial susceptibility was performed according to the Kirby-Bauer method. Results: The most frequent Shigella species was S. sonnei (49.2%), followed by S. flexneri (42.2%), S. boydii (7.9%) and S. dysenteriae (0.7%). Phase II (46.29%) was the most frequent serotype in S. sonnei, serotype 2a (43.61%) in S. flexneri, serotype 2 in S. boydii and serotype 4 in S. dysenteriae. High rates of resistance were detected for trimethoprim/sulfamethoxazole (91.0%), tetracycline (88.4%), ampicillin (73.9%) and chloramphenicol (64.9%), moderate rates for amoxicillin/clavulanic acid (25.1%), ciprofloxacin (16.7%) and nalidixic acid (14.8%), and low rates for cefotaxime (1.74%), nitrofurantoin (0.7%) and ceftazidime (0.6%). Moreover, antimicrobial resistance to fluoroquinolones increased considerably from 2017 to 2020. Conclusion: S. sonnei was the most frequent species, which have a large proportion of strains resistant to trimethoprim/sulfamethoxazole, and a growing trend of resistance to ciprofloxacin and nalidixic acid. This increase in resistance to commonly used antibiotics in treatments is alarming, threatening the control and management of these currently treatable infections.

Effect of source-tract acoustical coupling on the oscillation onset of the vocal folds.

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.

Effects of consonant manner and vowel height on intraoral pressure and articulatory contact at voicing offset and onset for voiceless obstruents.

In obstruent consonants, a major constriction in the upper vocal tract yields an increase in intraoral pressure (P(io)). Phonation requires that subglottal pressure (P(sub)) exceed P(io) by a threshold value, so as the transglottal pressure reaches the threshold, phonation will cease. This work investigates how P(io) 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 P(io) to clarify how supraglottal constrictions affect P(io). 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 P(io) before fricative-initial sequences than stop-initial sequences, and onset occurred at higher levels of P(io) 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 P(io)) 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.

A lumped mucosal wave model of the vocal folds revisited: recent extensions and oscillation hysteresis.

This paper examines an updated version of a lumped mucosal wave model of the vocal fold oscillation during phonation. Threshold values of the subglottal pressure and the mean (DC) glottal airflow for the oscillation onset are determined. Depending on the nonlinear characteristics of the model, an oscillation hysteresis phenomenon may occur, with different values for the oscillation onset and offset threshold. The threshold values depend on the oscillation frequency, but the occurrence of the hysteresis is independent of it. The results are tested against pressure data collected from a mechanical replica of the vocal folds, and oral airflow data collected from speakers producing intervocalic /h/. In the human speech data, observed differences between voice onset and offset may be attributed to variations in voice pitch, with a very small or inexistent hysteresis phenomenon.

Validation of theoretical models of phonation threshold pressure with data from a vocal fold mechanical replica.

This paper analyzes the capability of a mucosal wave model of the vocal fold to predict values of phonation threshold lung pressure. Equations derived from the model are fitted to pressure data collected from a mechanical replica of the vocal folds. The results show that a recent extension of the model to include an arbitrary delay of the mucosal wave in its travel along the glottal channel provides a better approximation to the data than the original version of the model, which assumed a small delay. They also show that modeling the vocal tract as a simple inertive load, as has been proposed in recent analytical studies of phonation, fails to capture the effect of the vocal tract on the phonation threshold pressure with reasonable accuracy.

Stop-consonant voicing and intraoral pressure contours in women and children.

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.

Analysis of facial motion patterns during speech using a matrix factorization algorithm.

This paper presents an analysis of facial motion during speech to identify linearly independent kinematic regions. The data consists of three-dimensional displacement records of a set of markers located on a subject's face while producing speech. A QR factorization with column pivoting algorithm selects a subset of markers with independent motion patterns. The subset is used as a basis to fit the motion of the other facial markers, which determines facial regions of influence of each of the linearly independent markers. Those regions constitute kinematic "eigenregions" whose combined motion produces the total motion of the face. Facial animations may be generated by driving the independent markers with collected displacement records.

Speech production variability in fricatives of children and adults: results of functional data analysis.

This study investigates token-to-token variability in fricative production of 5 year olds, 10 year olds, and adults. Previous studies have reported higher intrasubject variability in children than adults, in speech as well as nonspeech tasks, but authors have disagreed on the causes and implications of this finding. The current work assessed the characteristics of age-related variability across articulators (larynx and tongue) as well as in temporal versus spatial domains. Oral airflow signals, which reflect changes in both laryngeal and supralaryngeal apertures, were obtained for multiple productions of /h s z/. The data were processed using functional data analysis, which provides a means of obtaining relatively independent indices of amplitude and temporal (phasing) variability. Consistent with past work, both temporal and amplitude variabilities were higher in children than adults, but the temporal indices were generally less adultlike than the amplitude indices for both groups of children. Quantitative and qualitative analyses showed considerable speaker- and consonant-specific patterns of variability. The data indicate that variability in /s/ may represent laryngeal as well as supralaryngeal control and further that a simple random noise factor, higher in children than in adults, is insufficient to explain developmental differences in speech production variability.

Learning factor influence on the perceptual-auditory analysis. / Influência do fator de aprendizagem na análise perceptivo-auditiva.

PURPOSE: To investigate the learning factor during a perceptual-auditory analysis of an unusual task in three different groups. METHODS: 269 listeners, divided into three groups: 73 voice specialists Speech Language Pathologists (EG), 84 voice specialists Speech Language Pathologists (NEG); and 112 non-speech pathologists in the Naive Group (NG). They all completed a listening session that included 18 synthesized and 18 human voices with different types and degrees of deviation (50% of repetition for intra-rater consistency analysis). The task was to classify the voices as human or synthesized. We analyzed the learning factor by comparing the initial error percentage, first 18 voices, with the final, last 18 voices. RESULTS: EG presented less error towards the end of the task (25.5%) than at the beginning (28.6%) with statistical difference (p = 0.024). The error percentage of the beginning and the end of the task did not differ for the NEG and the NG (NEG beginning = 36.5%, end = 35.3%; NG beginning = 38.3%, end = 37.7%). CONCLUSION: The EG was the only group to present evidence of learning factor. Therefore, it seems that professional experience positively influences the perceptual-auditory analysis, which reinforces the impact of its training to become a voice specialist. Moreover, the voice specialists seem to be more prepared and more susceptible to use learning strategies to improve their performance during a perceptual-auditory analysis task, even if unusual.

OBJETIVO: Investigar o fator de aprendizagem durante uma tarefa perceptivo-auditiva para três grupos diferentes em uma tarefa não usual. MÉTODO: 269 ouvintes, divididos em três grupos: 73 no grupo dos fonoaudiólogos especialistas em voz (GE), 84 no grupo dos fonoaudiólogos não especialistas em voz (GNE) e 112 no grupo leigo (GL), dos não fonoaudiólogos. Todos foram submetidos a uma sessão de escuta que incluiu 18 vozes humanas e 18 vozes sintetizadas com diferentes tipos e graus de desvio, mais 50% de repetição para avaliar a consistência intraindivíduo. A tarefa era classificar as vozes como humana ou sintetizada. Analisou-se o fator de aprendizagem pela comparação da porcentagem de erros do começo, primeiras 18 vozes, e do final, últimas 18 vozes, da sessão de escuta. RESULTADOS: O GE foi submetido ao fator de aprendizagem, apresentando menos erros no final da tarefa (25,5%), do que no começo (28,6%), com diferença estatística (p = 0,024). O GNE e o GL não apresentaram diferença da porcentagem de erros no começo e no final da tarefa (GNE começo = 36,5%; GNE final = 35,3%; GL começo = 38,3%; GL final = 37,7%). CONCLUSÃO: O GE foi o único grupo que apresentou indícios evidentes do fator de aprendizagem. Parece que a experiência profissional influencia de modo positivo a análise perceptivo-auditiva, reforçando o impacto de um treinamento para se tornar um especialista em voz. Ainda, o especialista em voz parece estar mais preparado e mais suscetível a utilizar estratégias de aprendizagem para melhorar sua performance durante uma tarefa perceptivo-auditiva mesmo que pouco usual.

On the relation between the phonation threshold lung pressure and the oscillation frequency of the vocal folds.

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.

Perceptual Error Analysis of Human and Synthesized Voices.

OBJECTIVE/HYPOTHESIS: To assess the quality of synthesized voices through listeners' skills in discriminating human and synthesized voices. STUDY DESIGN: Prospective study. METHODS: Eighteen human voices with different types and degrees of deviation (roughness, breathiness, and strain, with three degrees of deviation: mild, moderate, and severe) were selected by three voice specialists. Synthesized samples with the same deviations of human voices were produced by the VoiceSim system. The manipulated parameters were vocal frequency perturbation (roughness), additive noise (breathiness), increasing tension, subglottal pressure, and decreasing vocal folds separation (strain). Two hundred sixty-nine listeners were divided in three groups: voice specialist speech language pathologists (V-SLPs), general clinician SLPs (G-SLPs), and naive listeners (NLs). The SLP listeners also indicated the type and degree of deviation. RESULTS: The listeners misclassified 39.3% of the voices, both synthesized (42.3%) and human (36.4%) samples (P = 0.001). V-SLPs presented the lowest error percentage considering the voice nature (34.6%); G-SLPs and NLs identified almost half of the synthesized samples as human (46.9%, 45.6%). The male voices were more susceptible for misidentification. The synthesized breathy samples generated a greater perceptual confusion. The samples with severe deviation seemed to be more susceptible for errors. The synthesized female deviations were correctly classified. The male breathiness and strain were identified as roughness. CONCLUSION: VoiceSim produced stimuli very similar to the voices of patients with dysphonia. V-SLPs had a better ability to classify human and synthesized voices. VoiceSim is better to simulate vocal breathiness and female deviations; the male samples need adjustment.

Perceptual Error Identification of Human and Synthesized Voices.

OBJECTIVES/HYPOTHESIS: To verify the discriminatory ability of human and synthesized voice samples. STUDY DESIGN: This is a prospective study. METHODS: A total of 70 subjects, 20 voice specialist speech-language pathologists (V-SLPs), 20 general SLPs (G-SLPs), and 30 naive listeners (NLs) participated of a listening task that was simply to classify the stimuli as human or synthesized. Samples of 36 voices, 18 human and 18 synthesized vowels, male and female (9 each), with different type and degree of deviation, were presented with 50% of repetition to verify intrarater consistency. Human voices were collected from a vocal clinic database. Voice disorders were simulated by perturbations of vocal frequency, jitter (roughness), additive noise (breathiness) and by increasing tension and decreasing separation of the vocal folds (strain). RESULTS: The average amount of error considering all groups was 37.8%, 31.9% for V-SLP, 39.3% for G-SLP, and 40.8% for NL. V-SLP had smaller mean percentage error for synthesized (24.7%), breathy (36.7%), synthesized breathy (30.8%), and tense (25%) and female (27.5%) voices. G-SLP and NL presented equal mean percentage error for all voices classification. All groups together presented no difference on the mean percentage error between human and synthesized voices (P value = 0.452). CONCLUSIONS: The quality of synthesized samples was very high. V-SLP presented a lower amount of error, which allows us to infer that auditory training assists on vocal analysis tasks.

Comparison of measures of variability of speech movement trajectories using synthetic records.

In speech research, it is often desirable to assess quantitatively the variability of a set of speech movement trajectories. This problem is studied here using synthetic trajectories, which consist of a common pattern and terms representing amplitude and phase variability. The results show that a technique for temporal alignment of the records based on functional data analysis allows us to extract the pattern and variability terms as separate functions, with good approximation. Indices of amplitude and phase variability are defined, which provide a more accurate assessment of variability than previous approaches.