Glottal Cycle Research Articles

Determination of glottal open regions by exploiting changes in the vocal tract system characteristics.

This paper presents an approach to determine the open phase region of a glottal cycle based on changes in the characteristics of the vocal tract system. The glottal closing phase contributes to major excitation of the vocal tract system. The opening phase affects the vocal tract system characteristics by effectively increasing the length of the tract, due to coupling of the subglottal region. To determine the glottal open region, it is necessary to estimate the vocal tract characteristics from the segment with subglottal coupling. The proposed method derives the dominant resonance frequency (DRF) of the vocal tract system at every sampling instant, using a heavily decaying window (HDW) for analysis. The DRF contour transits to lower frequencies during glottal open region, when compared to the glottal closed region. The open region, within the glottal cycles from voiced speech segment, is extracted using the HDW method. The results are compared with the open region derived from the electroglottograph (EGG) signals and speech signals. The results show that the proposed method based on DRF contour, derived from the speech signals, seems to perform better than the methods based on EGG signals.

Quantitative assessment of videolaryngostroboscopic images in patients with glottic pathologies

Introduction: Digital imaging techniques enable exploration of novel visualization modalities of the vocal folds during phonation and definition of parameters, facilitating more precise diagnosis of voice disorders.Aim: Application of computer vision algorithms for analysis of videolaryngostroboscopic (VLS) images aimed at qualitative and quantitative description of phonatory vibrations.Materials and methods: VLS examinations were conducted for 45 females, including 15 subjects with vocal nodules, 15 subjects with glottal incompetence, and 15 normophonic females. The recorded VLS images were preprocessed, the glottis area was segmented out, and the glottal cycles were identified. The glottovibrograms were built, and then the glottal area waveforms (GAW) were quantitatively described by computing the following parameters: open quotient (OQ), closing quotient (CQ), speed quotient (SQ), minimal relative glottal area (MRGA), and a new parameter termed closure difference index (CDI).Results: Profiles of the glottal widths assessed along the glottal length differentiated the study groups (P < 0.001). Moreover, it was shown that the OQ, CQ, CDI, and MRGA indices can be considered as viable parameters for quantifying kinematics of the vocal folds for normophonic subjects and patients with diagnosed vocal nodules and glottal incompetence (P < 0.001).Conclusions: Computer image processing and analysis methods applied to videolaryngostroboscopic images allow for their quantitative assessment. Computation of the size-related and time-related parameters characterizing glottic pathologies is of interest for evidence-based voice diagnostics. Results of the performed ROC curve analysis suggest that the evaluated parameters can distinguish patients with voice disorders from normophonic subjects.

Effects of Vocal Fold Nodules on Glottal Cycle Measurements Derived from High-Speed Videoendoscopy in Children.

The goal of this study is to quantify the effects of vocal fold nodules on vibratory motion in children using high-speed videoendoscopy. Differences in vibratory motion were evaluated in 20 children with vocal fold nodules (5–11 years) and 20 age and gender matched typically developing children (5–11 years) during sustained phonation at typical pitch and loudness. Normalized kinematic features of vocal fold displacements from the mid-membranous vocal fold point were extracted from the steady-state high-speed video. A total of 12 kinematic features representing spatial and temporal characteristics of vibratory motion were calculated. Average values and standard deviations (cycle-to-cycle variability) of the following kinematic features were computed: normalized peak displacement, normalized average opening velocity, normalized average closing velocity, normalized peak closing velocity, speed quotient, and open quotient. Group differences between children with and without vocal fold nodules were statistically investigated. While a moderate effect size was observed for the spatial feature of speed quotient, and the temporal feature of normalized average closing velocity in children with nodules compared to vocally normal children, none of the features were statistically significant between the groups after Bonferroni correction. The kinematic analysis of the mid-membranous vocal fold displacement revealed that children with nodules primarily differ from typically developing children in closing phase kinematics of the glottal cycle, whereas the opening phase kinematics are similar. Higher speed quotients and similar opening phase velocities suggest greater relative forces are acting on vocal fold in the closing phase. These findings suggest that future large-scale studies should focus on spatial and temporal features related to the closing phase of the glottal cycle for differentiating the kinematics of children with and without vocal fold nodules.

Jitter generation in voice signals produced by a two-mass stochastic mechanical model

Jitter is a phenomenon caused by the perturbation in the length of the glottal cycles due to the quasi-periodic oscillation of the vocal folds in the production of the voice. It can be modeled as a random phenomenon described by the deviations of the glottal cycle length in relation to a mean value. Its study has been developed due to important applications such as aid in identification of voices with pathological characteristics, when its values are large, because a normal voice has naturally a low level of jitter. The aim of this paper is to construct a stochastic model of jitter using a two-mass mechanical model of the vocal folds, assuming complete right-left symmetry of the vocal folds and considering the motion of the vocal folds only in the horizontal direction. The stiffnesses taken into account in the model are considered as stochastic processes and their modeling are proposed. Glottal signals and voice signals are generated with jitter and the probability density function of the fundamental frequency is constructed for several values of the hyperparameters that control the level of jitter.

Voice Signals Produced With Jitter Through a Stochastic One-mass Mechanical Model

The quasiperiodic oscillation of the vocal folds causes perturbations in the length of the glottal cycles, which are known as jitter. The observation of the glottal cycles variations suggests that jitter is a random phenomenon described by random deviations of the glottal cycle lengths in relation to a corresponding mean value and, in general, its values are expressed as a percentage of the duration of the glottal pulse. The objective of this paper is the construction of a stochastic model for jitter using a one-mass mechanical model of the vocal folds, which assumes complete right-left symmetry of the vocal folds, and which considers motions of the vocal folds only in the horizontal direction. The jitter has been the subject for researchers due to its important applications such as the identification of pathological voices (nodules in the vocal folds, paralysis of the vocal folds, or even, the vocal aging, among others). Large values for jitter variations can indicate a pathological characteristic of the voice. The corresponding stiffness of each vocal fold is considered as a stochastic process, and its modeling is proposed. The probability density function of the fundamental frequency related to the voice signals produced are constructed and compared for different levels of jitter. Some samples of synthesized voices in these cases are obtained. It is showed that jitter could be obtained using the model proposed. The Praat software was also used to verify the measures of jitter in the synthesized voice signals.

Time-Dependent Pressure and Flow Behavior of a Self-oscillating Laryngeal Model With Ventricular Folds

The purpose of the study was to better understand the pressure-flow behavior of a self-oscillating vocal fold model at various stages of the glottal cycle. An established self-oscillating vocal fold model was extended to include the false vocal folds (FVFs) and was used to study time-dependent pressure and velocity distributions through the larynx (including the true vocal folds [TVFs] and FVFs). Vocal fold vibration was modeled with a finite element method, laryngeal flow was simulated with the solution of unsteady Navier-Stokes equations, and the acoustics of the vocal tract was modeled with a wave reflection method. The results demonstrate realistic phonatory behaviors and therefore may be considered as a pedagogical tool for showing detailed aerodynamic, kinematic, and acoustic characteristics. The TVFs self-oscillated regularly with reasonable amplitude and mucosal waves. There were large pressure gradients in the glottal region. The centerline velocity was highest during glottal closing and sharply dropped near the center of the flow vortex. The average centerline velocity was about 25m/second in the glottal region. The transglottal pressure was higher during glottal closing when the glottal shape was divergent and pressure recovery was present within the glottis. The centerline velocity increased as expected throughout the convergent glottis, tended to decrease throughout the divergent glottis, and decreased past the TVFs within the ventricle-FVF region. This model produces realistic results and demonstrates interactions among phonation variables of a highly instructive nature, including the influence of the FVFs.

An Instrumental-Phonetic Justification for S bawayh's Classification of t ', q f and hamza as majh r Consonants

In his eighth-century treatise al-Kitāb the Baghdad-based Persian scholar Sībawayh divided the Arabic consonants into two classes, majhūr and mahmūs. The focus of this study is his inclusion of ṭāʾ, qāf and hamza among the majhūr consonants.2 Their classification has stimulated much discussion because while all other majhūr consonants are voiced, ṭāʾ and qāf are voiceless in Modern Standard Arabic (McCarus 2012), and there has been a general reluctance to describe hamza as voiced. We demonstrate that modern instrumental techniques of phonetic investigation, applied to Modern Standard Arabic (MSA) fuṣḥa style speech, can help us to make sense of Sībawayh's classification without having to assume either that he was mistaken about their voicing or that ṭāʾ and qāf were voiced at that time. Aerometric data from three speakers show that volume-velocity airflow at the release of majhūr stop consonants is much lower than for mahmūs stop consonants, and laryngographic and spectrographic analysis of the speech of eight speakers provides evidence that for ṭāʾ and qāf airflow is reduced by laryngeal adjustment while hamza is shown to be voiced, albeit typically with irregular glottal cycles. We relate our results to glottal states as described in Esling and Harris (2005), and conclude that the defining feature of majhūr consonants is low airflow regulated by glottal constrictions of various kinds and possibly also by reduced initiator power in the pulmonic airstream mechanism.

Vocal Fold Vibration in Vocal Fold Atrophy: Quantitative Analysis With High-Speed Digital Imaging

Vocal fold vibrations of vocal fold atrophy (VFA), a rapidly increasing voice disorder owing to worldwide societal aging, have not been clarified by high-speed digital imaging (HSDI). The HSDI method was performed on 46 patients (33 males and 13 females) with VFA and 20 vocally healthy subjects (8 males and 12 females), and the obtained data were quantitatively evaluated by frame-by-frame analysis, laryngotopography, single- and multi-line kymography, and glottal area waveform. Overall, patients with VFA revealed larger open quotients, larger lateral phase difference, larger integral glottal width (the average glottal width over a glottal cycle), and smaller speed index than vocally healthy subjects. Some gender difference was noted: in males, lateral phase difference was not significant; and in females, integral glottal width and speed index were not significant. Correlation study revealed moderate correlations between HSDI-derived parameters and conventional acoustic or aerodynamic parameters. The combination of multiple HSDI analysis methods was effective in documenting the characteristics of vocal fold vibrations in VFA. The knowledge of general vibratory characteristics and gender difference is beneficial for the appropriate clinical care of VFA.

Estimation of inferior-superior vocal fold kinematics from high-speed stereo endoscopic data in vivo.

Despite being an indispensable tool for both researchers and clinicians, traditional endoscopic imaging of the human vocal folds is limited in that it cannot capture their inferior-superior motion. A three-dimensional reconstruction technique using high-speed video imaging of the vocal folds in stereo is explored in an effort to estimate the inferior-superior motion of the medial-most edge of the vocal folds under normal muscle activation in vivo. Traditional stereo-matching algorithms from the field of computer vision are considered and modified to suit the specific challenges of the in vivo application. Inferior-superior motion of the medial vocal fold surface of three healthy speakers is reconstructed over one glottal cycle. The inferior-superior amplitude of the mucosal wave is found to be approximately 13 mm for normal modal voice, reducing to approximately 3 mm for strained falsetto voice, with uncertainty estimated at σ ≈ 2 mm and σ ≈ 1 mm, respectively. Sources of error, and their relative effects on the estimation of the inferior-superior motion, are considered and recommendations are made to improve the technique.

Combining differentiated electroglottograph and differentiated audio signals to reliably measure vocal fold closed quotient

Over the past few decades researchers have explored the use of the electroglottograph (EGG) as a non-invasive method for representing vocal fold contact during vowel production and to measure the closed quotient (CQ) and open quotient (OQ) of the glottal cycle. The first derivative of the EGG signal (dEGG) can be used to indicate these moments (Childers & Krishnamurthy, 1985). However, there can be double positive peaks in the dEGG as well as a variety of negative peak patterns (Herbst et al., 2010). Obviously these variations will alter any measurements made from the signal. Recently, the use of the dEGG with dAudio signal was reported as a means for more reliable measurement of the CQ from the EGG signal in combination with a time synchronized audio signal. The purpose of this study is to demonstrate the reliability of the dEGG and dAudio for determining CQ across a variety of vocal conditions. Files recorded from group of 15 trained females singing an octave that included their primo passaggio provided the data. Preliminary results indicate high reliability of the CQ measurements in both the chest and middle registers of all of the singers.

Analysis of production characteristics of laughter

In this paper, the production characteristics of laughter are analysed at call and bout levels. Data of natural laughter is examined using electroglottograph (EGG) and acoustic signals. Nonspeech-laugh and laughed-speech are analysed in comparison with normal speech using features derived from the EGG and acoustic signals. Analysis of EGG signal is used to derive the average closed phase quotient in glottal cycles and the average instantaneous fundamental frequency (F0). Excitation source characteristics are analysed from the acoustic signal using a modified zero-frequency filtering (mZFF) method. Excitation impulse density and the strength of impulse-like excitation are extracted from the mZFF signal. Changes in the vocal tract system characteristics are examined in terms of the first two dominant frequencies derived using linear prediction (LP) analysis. Additional excitation information present in the acoustic signal is examined using a measure of sharpness of peaks in the Hilbert envelope of the LP residual at the glottal closure instants. Parameters representing degree of change and temporal changes in the production features are also derived to study the discriminating characteristics of laughter from normal speech. Changes are larger for nonspeech-laugh than laughed-speech, with reference to normal speech.

On the jet formation through a leaky glottis

The present experimental study aims at analyzing the jet formation of the glottal jet flow using a model of a leaky glottis. Experiments were performed in a flow channel with dynamic models of the vocal folds in order to measure the glottal waveform and the velocity distribution in the supraglottal region using High Speed Particle Image Velocimetry (HSPIV). Proper Orthogonal Decomposition (POD) of the vortex Q-criterion was performed in order to detect the energetically most significant large-scale vortex structures and their appearance in the jet flow. The spectral analysis of the glottal waveforms results in an increased spectral decay with more prominent peaks at higher frequencies in the case of a leaky glottis compared to a completely closing reference case. Vortex induced fluctuation frequencies have similar spectral content in both cases as they appear as trains of vortex packets in a regular manner over the glottal cycle. However, when removing the false vocal folds in the leaky glottis model, coherence of vortex generation is lost over the motion cycle. Thus, the presence of the false vocal folds retains most of the vortex induced characteristics in the source spectrum even when the vocal folds do not close fully.

Age- and Gender-Related Difference of Vocal Fold Vibration and Glottal Configuration in Normal Speakers: Analysis With Glottal Area Waveform

Glottal area waveform (GAW) analysis is widely used in the assessment of vocal fold vibration by high-speed digital imaging (HSDI). Because normative GAW data obtained from a large number of subjects have not been reported, we conducted a prospective study to obtain normative results for GAW analysis of HSDI findings and clarify normal variations associated with gender and age. Vocally healthy adults were divided into a young group (aged≤35years) and an elderly group (aged≥65years). The configuration and size of the glottal area were assessed at different phases of the glottal cycle, and gender- and age-related differences were evaluated. A total of 26 young subjects (nine men and 17 women; mean age: 27years) and 20 elderly subjects (eight men and 12 women; mean age: 73years) were investigated. The glottal area at different points of the glottal cycle showed a negative correlation with frequency. Although the GAW parameters of young women appeared to be different from those of the other subgroups, the differences were not statistically significant. Young women predominantly had a triangular- or vase-shaped glottal configuration at all frequencies, whereas the other subgroups showed various glottal shapes. The present study clarified gender- and age-related differences of GAW parameters obtained with HSDI. Young women were likely to show different glottal configurations and different responses to frequency changes from those of young men, elderly men, and elderly women. Phonosurgeons should pay attention to the normal variations detected in the present study.

Improvement of Vocal Pathologies Diagnosis Using High-Speed Videolaryngoscopy

Introduction The study of the dynamic properties of vocal fold vibration is important for understanding the vocal production mechanism and the impact of organic and functional changes. The advent of high-speed videolaryngoscopy (HSV) has provided the possibility of seeing the real cycle of vocal fold vibration in detail through high sampling rate of successive frames and adequate spatial resolution. Objective To describe the technique, advantages, and limitations of using HSV and digital videokymography in the diagnosis of vocal pathologies. Methods We used HSV and digital videokymography to evaluate one normophonic individual and four patients with vocal fold pathologies (nodules, unilateral paralysis of the left vocal fold, intracordal cyst, and adductor spasmodic dysphonia). The vocal fold vibration parameters (glottic closure, vibrational symmetry, periodicity, mucosal wave, amplitude, and glottal cycle phases) were assessed. Results Differences in the vocal vibration parameters were observed and correlated with the pathophysiology. Conclusion HSV is the latest diagnostic tool in visual examination of vocal behavior and has considerable potential to refine our knowledge regarding the vocal fold vibration and voice production, as well as regarding the impact of pathologic conditions have on the mechanism of phonation.

Measurement of Glottal Cycle Characteristics Between Children and Adults: Physiological Variations

The aim of this study was to quantify phases of the vibratory cycle using measurements of glottal cycle quotients and glottal cycle derivatives, in typically developing prepubertal children and young adults with the use of high-speed digital imaging (HSDI). Vocal fold vibrations were recorded from 27 children (age range 5-9 years) and 35 adults (age range 21-45years), with HSDI at 4000 frames per second for sustained phonation. Glottal area waveform measures of Open Quotient, Closing Quotient, Speed Index (SI), Rate Quotient, and Asymmetry Quotient (AsyQ) were computed. Glottal cycle derivatives of Amplitude Quotient (AQ) and Maximum Area Declination Rate (MADR) were also computed. Group differences (adult females, adult males, and children) were statistically investigated for mean and standard deviation values of the glottal cycle quotients and glottal cycle derivatives. Children exhibited higher values of SI and AsyQ and lower values of MADR compared with adult males. Children exhibited the highest mean value and lowest variability in AQ compared with adult males and females. Adult males showed lower values of SI, AsyQ, AQ, and higher values of MADR compared with adult females. Glottal cycle vibratory motion in children is functionally different compared with adult males and females, suggesting the need for development of children specific norms for both normal and disordered voice qualities.

Glottal opening and closing events investigated by electroglottography and super-high-speed video recordings

Previous research has suggested that the peaks in the first derivative (dEGG) of the electroglottographic (EGG) signal are good approximate indicators of the events of glottal opening and closing. These findings were based on high-speed video (HSV) recordings with frame rates 10 times lower than the sampling frequencies of the corresponding EGG data. The present study attempts to corroborate these previous findings, utilizing super-HSV recordings. The HSV and EGG recordings (sampled at 27 and 44 kHz, respectively) of an excised canine larynx phonation were synchronized by an external TTL signal to within 0.037 ms. Data were analyzed by means of glottovibrograms, digital kymograms, the glottal area waveform and the vocal fold contact length (VFCL), a new parameter representing the time-varying degree of 'zippering' closure along the anterior-posterior (A-P) glottal axis. The temporal offsets between glottal events (depicted in the HSV recordings) and dEGG peaks in the opening and closing phase of glottal vibration ranged from 0.02 to 0.61 ms, amounting to 0.24-10.88% of the respective glottal cycle durations. All dEGG double peaks coincided with vibratory A-P phase differences. In two out of the three analyzed video sequences, peaks in the first derivative of the VFCL coincided with dEGG peaks, again co-occurring with A-P phase differences. The findings suggest that dEGG peaks do not always coincide with the events of glottal closure and initial opening. Vocal fold contacting and de-contacting do not occur at infinitesimally small instants of time, but extend over a certain interval, particularly under the influence of A-P phase differences.

Intraglottal geometry and velocity measurements in canine larynges

Previous flow velocity measurements during phonation in canine larynges were done above the glottal exit. These studies found that vortical structures are present in the flow above the glottis at different phases of the glottal cycle. Some vortices were observed to leave the glottis during the closing phase and assumptions were proposed regarding their formation mechanism. In the current study, intraglottal velocity measurements are performed using PIV, and the intraglottal flow characteristics are determined. Results from five canine larynges show that at low subglottal pressure the glottis assumes a minimal divergence angle during closing and the flow separates at the glottal exit. Vortical structures are observed above the glottis but not inside. As the subglottal pressure is increased, the divergence angle between the folds during closing increases and the location of the flow separation moves upstream into the glottis. Entrainment flow enters the glottis to fill the void that is formed between the glottal jet and the fold. Vortical structures develop near the superior edge at medium and high subglottal pressures from the flow separation. The magnitude of their swirling strength changes as a function of the wall dynamics.

Graphical Evaluation of Vocal Fold Vibratory Patterns by High-Speed Videolaryngoscopy

To characterize the voice and vocal fold function of an individual, it is essential to evaluate vocal fold vibration. The most widely used method for this purpose has been videolaryngoscopy. This article proposes a digital image processing algorithm to estimate the glottal area (ie, the space between the vocal folds) and produce graphs of the opening and closing phases of the glottal cycle. In eight subjects without voice disorders, vocal fold movements were recorded by high-speed videolaryngoscopy at 4000 frames per second. The video data were processed by a combination of image segmentation techniques that estimate the glottal area. The segmented area was used to construct the glottal waveform. The graphs revealed important properties of vocal fold vibration, including amplitude, velocity, and other characteristics that have a major influence on voice quality. The combination of the high-speed technology with the proposed method improves the vocal fold analysis given a numerical feedback through graphical representation of the real vibratory patterns of the folds.

Assessment of the short-term effects of endotracheal intubation on vocal functions

EnAbstract Background Transient voice change associated with endotracheal intubation has generally been attributed to vocal fold trauma. Aim The aim of this study was to examine the effects of short-term endotracheal intubation on the vocal fold vibratory pattern using videokymography in order to aid the early detection and prevention of these changes. Participants and methods This study was carried out on 40 patients who were scheduled for a variety of elective surgical procedures under general anesthesia. They were 26 males, ranging in age from 17 to 61 years, mean age of 36.4±4.2 years, and 14 females ranging in age from 16 to 54 years, mean age of 34.6±5.3 years. Evaluation of vocal functions was carried out at three intervals, 1 day before intubation, 1 day after extubation, and 1 week later. All patients were subjected to analysis of their complaints, auditory perceptual assessment of their voice, and assessment of vocal fold vibration using videokymography. Results Sixteen patients complained of postoperative voice change, ranging in severity from good in 11, moderate in four, and bad in one patient. After 1 week, five patients were still complaining of voice change, ranging from good in four to moderate in one. There was a positive significant correlation between the degree of voice change and both the duration of anesthesia and tube size. There was postextubation mild to moderate voice change in 12 patients. The pitch was decreased in nine patients, increased in two patients, and there was diplophonia in one patient. The loudness was fluctuating in eight patients and was decreased in four patients; after 1 week, there was an improvement in all the perceived parameters; however, persistent dysphonia was perceived in three patients. There was a positive significant correlation between the degree of dysphonia and both the duration of anesthesia and the tube size. The normal video mode of videokymography, performed 1 day after extubation, indicated evidence of traumatic laryngeal lesions in 15 patients. In the high-speed mode of videokymography performed before intubation, 1 day after extubation, and 1 week after extubation, a significant difference was found in most of the parameters when comparing before intubation and 1 day after extubation; also, a significant difference in all the parameters was found 1 day after extubation and 1 week after extubation, whereas a nonsignificant difference was found when comparing before intubation and 1 week after extubation. There was a significant positive correlation between both the duration of intubation and the tube size with the severity of voice complaint and grade of dysphonia. Also, there was a significant positive correlation between the aperiodicity in both the amplitude of mucosal wave and the glottal cycle time, and both the duration of intubation and the tube size in the dysphonic group. Conclusion Traumatic lesions of the laryngeal structures that occur during intubation, in addition to possible subepithelial changes, are the most common causes of postoperative dysphonia, with a tendency toward a regressive course of the resulting dysphonia. As such, it is important to establish an early diagnosis and adopt preventive measures.

Three-dimensional laryngeal flow fields induced by a model vocal fold polyp

Pathological laryngeal flow fields are investigated in a dynamically-driven, scaled-up model of the vocal folds. Disruption of the flow field due to the presence of a geometric protuberance, representative of a sessile unilateral polyp, is investigated in both the streamwise and transverse flow directions using phase-averaged particle image velocimetry. It is shown that the protuberance disrupts the normal flow behavior of the glottal jet throughout the phonatory cycle. During the divergent portions of the glottal cycle, the flow is characterized by the formation of hairpin vortices downstream of the protuberance. The protuberance also introduces significant velocity gradients in the anterior-posterior direction, which cover ∼30−40% of the vocal fold length. It is proposed that the disruption of the normal velocity behavior owing to the presence of a polyp will adversely impact the aerodynamic loadings that drive vocal fold motion, contributing to the temporal and spatial vocal fold asymmetries that are clinically-observed in patients with unilateral polyps.