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.

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.

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.

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.

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.

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

RESUMO 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.

ABSTRACT 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.

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.

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.

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.

Prevalencia y factores asociados con la filariosis por Mansonella ozzardi en 2 comunidades periurbanas de Iquitos, 2009 / Prevalence of filariasis by Mansonella ozzardi and associated factors among 2 suburban communities of Iquitos, 2009

Introducción: Tres casos de infección por Mansonella ozzardi (M. ozzardi) en muestras de malaria que provenían de 2 comunidades periurbanas de Iquitos (Perú) dieron la sospecha de transmisión local. El objetivo del estudio fue determinar la prevalencia y factores asociados con la filariosis por M. ozzardi en estas comunidades. Materiales y métodos: Se realizó un estudio transversal en las comunidades de Laguna Azul y La Unión en Iquitos. A todos los pobladores se les tomó una gota gruesa para la detección de M. ozzardi y se les realizó una encuesta epidemiológica. Se realizó colecta de larvas y mosquitos para identificación de potenciales vectores. Se calcularon los OR ajustados (ORa) usando regresión logística múltiple. Resultados: Se evaluaron a 433 personas; 58% fueron mujeres; la mediana de edad fue de 20 años; 58,2% fueron migrantes, 3,7% pescadores y 12,9% habían viajado por las cuencas del Alto anay. La prevalencia de M. ozzardi fue de 1,4% (6/433) y el más joven de los casos tuvo 31 años; se encontró asociación con ser pescador (ORa: 8,7; IC 95: 1,1-76,0) y con haber realizado viajes por la cuenca del Alto Nanay (ORa: 11,2; IC 95: 1,2-112,5). No se evidenció densidad significativa de vectores simúlidos o culicoides. Conclusión: Las comunidades estudiadas tuvieron una baja prevalencia de M. ozzardi y por la edad de los casos y los factores asociados encontrados se sospecha infección foránea a la zona de estudio, en especial en la cuenca del Alto Nanay.

Introduction: Three cases of M. ozzardi infection from 2 suburban communities in Iquitos, Peru, led to a suspicion of local transmission. The objective of the study was to determine the prevalence of filariasis by M. ozzardi and its associated factors among these communities. Materials and methods: A cross-sectional study was performed, as well as an epidemiological survey and a thick smear blood test. Larvae and mosquitoes were collected. The adjusted OR (aOR) using multiple logistic regression was calculated. Results: A total of 433 participants were enrolled; 58% were women. The prevalence of M. ozzardi was 1.4% and the associated factors included being a fisherman (aOR: 8.7; 95%CI: 1.1-76.0) and being on the Alto Nanay river (aOR: 11.2; 95%CI: 1.2-112.5). No significant evidence of simulidos or culicoides was found. Conclusion: The low prevalence of M. ozzardi found suggests a foreign infection, probably derived from the Alto Nanay river.

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.

Testing the reliability of Grade, Roughness and Breathiness scores by means of synthetic speech stimuli.

This article describes a synthesizer of disordered voices and reports a test of the reliability of Grade, Roughness, and Breathiness scores assigned to synthetic stimuli by eight expert listeners in two sessions. Speech stimuli [a], [i], [u], [ai], and [ia] were synthesized with three values of vocal frequency and four levels of vocal jitter and pulsatile additive noise each. The agreement and correlation of scores assigned by the same rater in different sessions, or by different raters in the same session, accord with published data. Only a small part of the variance of the arithmetic differences between the scores that are assigned to the same stimulus is explained by the stimuli properties. The conclusion is that differences between scores that are assigned to the same stimulus are not attributable to biases of individual raters; such biases would shift all the scores assigned on a scale, and the shift would be interpretable in terms of the properties of the stimuli.

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.

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.

[Process of construction of the national research agenda on Human Resources in Health in Peru 2011 - 2014]. / Proceso de construcción de la agenda nacional de investigación sobre Recursos Humanos en Salud (RHUS) en el Perú, 2011-2014.

The National Health Authority of Peru, as part of the implementation of national priorities for health research in 2010 developed the process of building the national research agenda on health manpower (HM). In a scenario of technical challenges, national and international policy and under a nation-wide participatory approach with key stakeholders in the health system, training and aid HM linked to the subject, establishing a socially agreed agenda. Process consists of 3 phases: 1. National review of evidence and relevant information on RHUS, 2. Consultation with opinion leaders and subject experts, and 3. A collaborative space (national workshop) of deliberation, consensus and legitimacy of the agenda. Finally, we present the agenda consists of 30 research topics on health manpower, to be developed in the period 2011- 2014, and raises the challenges and prospects for implementation.

Proceso de construcción de la agenda nacional de investigación sobre Recursos Humanos en Salud (RHUS) en el Perú, 2011-2014 / Process of construction of the national research agenda on Human Resources in Health in Peru 2011 - 2014

La Autoridad Sanitaria Nacional del Perú, como parte del proceso de implementación de las prioridades nacionales de investigación en salud en el 2010, desarrolló el proceso de construcción de la agenda nacional de investigación sobre recursos humanos en salud (RHUS). En un escenario de desafíos técnico-políticos nacionales e internacionales y bajo un enfoque participativo de alcance nacional, con actores clave del sistema de salud, formación de RHUS y cooperantes vinculados con el tema, se establece una agenda socialmente consensuada. El proceso consta de tres fases: 1. Revisión nacional de evidencias e información relevante sobre RHUS; 2. Consulta a líderes de opinión y expertos temáticos y 3. Un espacio participativo (taller nacional) de deliberación, consenso y legitimación de la agenda. Finalmente se presenta la agenda compuesta por 30 temas de investigación sobre RHUS para ser desarrolladas en el período 2011-2014 y se plantean los retos y perspectivas para su implementación.

The National Health Authority of Peru, as part of the implementation of national priorities for health research in 2010 developed the process of building the national research agenda on health manpower (HM). In a scenario of technical challenges, national and international policy and under a nation-wide participatory approach with key stakeholders in the health system, training and aid HM linked to the subject, establishing a socially agreed agenda. Process consists of 3 phases: 1. National review of evidence and relevant information on RHUS, 2. Consultation with opinion leaders and subject experts, and 3. A collaborative space (national workshop) of deliberation, consensus and legitimacy of the agenda. Finally, we present the agenda consists of 30 research topics on health manpower, to be developed in the period 2011- 2014, and raises the challenges and prospects for implementation.

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.