Glottal Airflow Research Articles

Survival in Vivo Canine Phonation Model Without Stimulation.

We describe a survival nonstimulated in vivo canine phonation model using distending laryngoscope, cramp frame, and constant humidified glottal airflow to elicit phonation. Five beagle dogs were involved in this study. One cuffed endotracheal tube was placed below the glottis through the tracheotomy and delivered humidified airflow to the glottis. Arytenoids approximation was maintained using a clamp under the distending laryngoscope. Acoustic and aerodynamic parameters were measured using synchronous signal collection system and analysis software. Vocal oscillation also was examined using stroboscope laryngeal imaging. For the nonstimulated in vivo phonation animal, the sound intensity and fundamental frequency were 78.3 ± 6.8 dB and 127.6 ± 29.2 Hz in the first experiment and 82.9 ± 6.6 dB and 175.2 ± 4.4 Hz 4 weeks later. The aerodynamic analysis revealed the mean subglottal phonation threshold pressure (PTP) and phonation threshold flow (PTF) were 8.5 ± 4.0 cmH20 and 683.0 ± 356.4 mL/s in the first experiment and 16.1 ± 8.6 cmH20 and 384.8.0 ± 230.6 mL/s in the second experiment 4 weeks later. Stroboscope image revealed sustained vocal vibration during great airflow delivery to glottis in the phonation animal model. We developed a survival nonstimulated in vivo phonation canine model that allows the study of long-term animal phonation study as its own control.

Effect of Bhramari Pranayama on the Acoustic and Aerodynamic Parameters of Voice in Normophonic Females.

Summary. Objective Pranayama is known for improving various health conditions. The present study is aimed at investigating the effects of bhramari pranayama on aerodynamic and acoustic parameters of voice in healthy individuals. Study Design This is a pretest-posttest design study. Methods A total of 24 participants in the age range of 20 to 25 years completed the bhramari pranayama regimen for 30 sessions. Aerodynamic and acoustic assessments were done before and after pranayama sessions. Maximum phonation duration, pitch, loudness, subglottal pressure, glottal airflow, laryngeal resistance and conductance along with acoustical parameters such as average F0, jitter, and shimmer, soft phonation index, noise to harmonic ratio, cepstral peak prominence, and smoothened cepstral peak prominence were analysed. Results The results revealed significant improvement in the maximum phonation duration, glottal airflow and pressure, average fundamental frequency, and cepstral peak prominence after practice suggesting that it has an effect on voice parameters. Conclusion Bhramari pranayama is effective in improving the acoustic and aerodynamic parameters of voice. The same needs to be investigated in hyper- and hypofunctional voice disorders in the future studies.

Estimation of Source-Filter Interaction Regions Based on Electroglottography

Source-filter interaction is a phenomenon in which acoustic airway pressures influence the glottal airflow at the source (level 1) and the vibration pattern of the vocal folds (level 2). This interaction is most significant when dominant source harmonics are near airway resonances. The influence of acoustic airway pressures on vocal fold vibration (level 2) was studied systematically by changing the supraglottal vocal tract length in human subjects with tube extensions. The subjects were asked to perform fundamental frequency (fo) glides while phonating through tubes of various lengths. An algorithm was developed using the quasi-open quotient extracted from the electroglottograph. Regions of sudden vocal fold vibration pattern change due to source-filter interaction were inferred from contact area changes. The algorithm correctly identified 89% of male and 84.8% of female quantal changes in contact pattern associated with interactions between source harmonics and formants during ascending glides. During the descending glides, the algorithm correctly identified 84% of male and 81.1% of female quantal changes in contact pattern. These results are in comparison with those obtained from the fo-based algorithm (Maxfield etal).

Magnitude of Neck-Surface Vibration as an Estimate of Subglottal Pressure During Modulations of Vocal Effort and Intensity in Healthy Speakers.

This study examined the relationship between the magnitude of neck-surface vibration (NSVMag; transduced with an accelerometer) and intraoral estimates of subglottal pressure (P'sg) during variations in vocal effort at 3 intensity levels. Twelve vocally healthy adults produced strings of /pɑ/ syllables in 3 vocal intensity conditions, while increasing vocal effort during each condition. Measures were made of P'sg (estimated during stop-consonant closure), NSVMag (measured during the following vowel), sound pressure level, and respiratory kinematics. Mixed linear regression was used to analyze the relationship between NSVMag and P'sg with respect to total lung volume excursion, levels of lung volume initiation and termination, airflow, laryngeal resistance, and vocal efficiency across intensity conditions. NSVMag was significantly related to P'sg (p < .001), and there was a significant, although small, interaction between NSVMag and intensity condition. Total lung excursion was the only additional variable contributing to predicting the NSVMag-P'sg relationship. NSVMag closely reflects P'sg during variations of vocal effort; however, the relationship changes across different intensities in some individuals. Future research should explore additional NSV-based measures (e.g., glottal airflow features) to improve estimation accuracy during voice production.

Parameterization of a computational physical model for glottal flow using inverse filtering and high-speed videoendoscopy

High-speed videoendoscopy, glottal inverse filtering, and physical modeling can be used to obtain complementary information about speech production. In this study, the three methodologies are combined to pursue a better understanding of the relationship between the glottal air flow and glottal area. Simultaneously acquired high-speed video and glottal inverse filtering data from three male and three female speakers were used. Significant correlations were found between the quasi-open and quasi-speed quotients of the glottal area (extracted from the high-speed videos) and glottal flow (estimated using glottal inverse filtering), but only the quasi-open quotient relationship could be represented as a linear model. A simple physical glottal flow model with three different glottal geometries was optimized to match the data. The results indicate that glottal flow skewing can be modeled using an inertial vocal/subglottal tract load and that estimated inertia within the glottis is sensitive to the quality of the data. Parameter optimisation also appears to favour combining the simplest glottal geometry with viscous losses and the more complex glottal geometries with entrance/exit effects in the glottis.

Glottal Aerodynamic Measures in Women With Phonotraumatic and Nonphonotraumatic Vocal Hyperfunction.

The purpose of this study was to determine the validity of preliminary reports showing that glottal aerodynamic measures can identify pathophysiological phonatory mechanisms for phonotraumatic and nonphonotraumatic vocal hyperfunction, which are each distinctly different from normal vocal function. Glottal aerodynamic measures (estimates of subglottal air pressure, peak-to-peak airflow, maximum flow declination rate, and open quotient) were obtained noninvasively using a pneumotachograph mask with an intraoral pressure catheter in 16 women with organic vocal fold lesions, 16 women with muscle tension dysphonia, and 2 associated matched control groups with normal voices. Subjects produced /pae/ syllable strings from which glottal airflow was estimated using inverse filtering during /ae/ vowels, and subglottal pressure was estimated during /p/ closures. All measures were normalized for sound pressure level (SPL) and statistically tested for differences between patient and control groups. All SPL-normalized measures were significantly lower in the phonotraumatic group as compared with measures in its control group. For the nonphonotraumatic group, only SPL-normalized subglottal pressure and open quotient were significantly lower than measures in its control group. Results of this study confirm previous hypotheses and preliminary results indicating that SPL-normalized estimates of glottal aerodynamic measures can be used to describe the different pathophysiological phonatory mechanisms associated with phonotraumatic and nonphonotraumatic vocal hyperfunction.

Evaluation of Glottal Inverse Filtering Algorithms Using a Physiologically Based Articulatory Speech Synthesizer.

Glottal inverse filtering aims to estimate the glottal airflow signal from a speech signal for applications such as speaker recognition and clinical voice assessment. Nonetheless, evaluation of inverse filtering algorithms has been challenging due to the practical difficulties of directly measuring glottal airflow. Apart from this, it is acknowledged that the performance of many methods degrade in voice conditions that are of great interest, such as breathiness, high pitch, soft voice, and running speech. This paper presents a comprehensive, objective, and comparative evaluation of state-of-the-art inverse filtering algorithms that takes advantage of speech and glottal airflow signals generated by a physiological speech synthesizer. The synthesizer provides a physics-based simulation of the voice production process and thus an adequate test bed for revealing the temporal and spectral performance characteristics of each algorithm. Included in the synthetic data are continuous speech utterances and sustained vowels, which are produced with multiple voice qualities (pressed, slightly pressed, modal, slightly breathy, and breathy), fundamental frequencies, and subglottal pressures to simulate the natural variations in real speech. In evaluating the accuracy of a glottal flow estimate, multiple error measures are used, including an error in the estimated signal that measures overall waveform deviation, as well as an error in each of several clinically relevant features extracted from the glottal flow estimate. Waveform errors calculated from glottal flow estimation experiments exhibited mean values around 30% for sustained vowels, and around 40% for continuous speech, of the amplitude of true glottal flow derivative. Closed-phase approaches showed remarkable stability across different voice qualities and subglottal pressures. The algorithms of choice, as suggested by significance tests, are closed-phase covariance analysis for the analysis of sustained vowels, and sparse linear prediction for the analysis of continuous speech. Results of data subset analysis suggest that analysis of close rounded vowels is an additional challenge in glottal flow estimation.

Comparison of Effects Produced by Physiological Versus Traditional Vocal Warm-up in Contemporary Commercial Music Singers

The present study aimed to observe whether physiological warm-up and traditional singing warm-up differently affect aerodynamic, electroglottographic, acoustic, and self-perceived parameters of voice in Contemporary Commercial Music singers. Thirty subjects were asked to perform a 15-minute session of vocal warm-up. They were randomly assigned to one of two types of vocal warm-up: physiological (based on semi-occluded exercises) or traditional (singing warm-up based on open vowel [a:]). Aerodynamic, electroglottographic, acoustic, and self-perceived voice quality assessments were carried out before (pre) and after (post) warm-up. No significant differences were found when comparing both types of vocal warm-up methods, either in subjective or in objective measures. Furthermore, the main positive effect observed in both groups when comparing pre and post conditions was a better self-reported quality of voice. Additionally, significant differences were observed for sound pressure level (decrease), glottal airflow (increase), and aerodynamic efficiency (decrease) in the traditional warm-up group. Both traditional and physiological warm-ups produce favorable voice sensations. Moreover, there are no evident differences in aerodynamic and electroglottographic variables when comparing both types of vocal warm-ups. Some changes after traditional warm-up (decreased intensity, increased airflow, and decreased aerodynamic efficiency) could imply an early stage of vocal fatigue.

Alternating minimisation for glottal inverse filtering

A new method is proposed for solving the glottal inverse filtering (GIF) problem. The goal of GIF is to separate an acoustical speech signal into two parts: the glottal airflow excitation and the vocal tract filter. To recover such information one has to deal with a blind deconvolution problem. This ill-posed inverse problem is solved under a deterministic setting, considering unknowns on both sides of the underlying operator equation. A stable reconstruction is obtained using a double regularization strategy, alternating between fixing either the glottal source signal or the vocal tract filter. This enables not only splitting the nonlinear and nonconvex problem into two linear and convex problems, but also allows the use of the best parameters and constraints to recover each variable at a time. This new technique, called alternating minimization glottal inverse filtering (AM-GIF), is compared with two other approaches: Markov chain Monte Carlo glottal inverse filtering (MCMC-GIF), and iterative adaptive inverse filtering (IAIF), using synthetic speech signals. The recent MCMC-GIF has good reconstruction quality but high computational cost. The state-of-the-art IAIF method is computationally fast but its accuracy deteriorates, particularly for speech signals of high fundamental frequency (F0). The results show the competitive performance of the new method: With high F0, the reconstruction quality is better than that of IAIF and close to MCMC-GIF while reducing the computational complexity by two orders of magnitude.

Uncertainty of glottal airflow estimation during continuous speech using impedance-based inverse filtering of the neck-surface acceleration signal

The aim of this work is to determine the uncertainty of non-invasive glottal aerodynamic measures that are obtained using subglottal impedance-based inverse filtering (IBIF) of the signal from a neck-placed accelerometer during continuous speech. Currently, we are studying the vocal behavior of individuals with typical voices and voice disorders by analyzing weeklong recordings using a smartphone-based ambulatory voice monitor. We extend on previously reported analyses of sustained vowel production using subglottal IBIF and move toward continuous speech applications where IBIF parameters are estimated in a frame-based approach. Selected voiced frames of both oral-airflow (baseline) and acceleration signal from the Rainbow Passage are used to build a probabilistic model of IBIF parameters to run multiple random realizations of the inverse-filtered neck-surface acceleration signal. Confidence intervals are estimated for both the glottal waveform and derived features. The probabilistic model is tested using data from patients with vocal hyperfunction and matched-control subjects with normal voices at a comfortable pitch and loudness in an acoustically treated sound booth. Results show that model parameters follow approximately normal distributions, and the confidence intervals for the estimates of glottal aerodynamic measures were &amp;lt;10%, which is in close agreement with previously reported IBIF performance using sustained vowels.

Whisper and Phonation: Aerodynamic Comparisons Across Adduction and Loudness

Whisper is known to be produced by different speakers differently, especially with respect to glottal configuration that influences glottal aerodynamics. Differences in whisper production and phonation types imply important linguistic information in many languages, are identified in vocal pathologies, are used to communicate mood and emotion, and are used in vocal performance. The present study focused on investigating the aerodynamic differences between whisper and phonation at different loudness and adduction levels. Three men and five women between 20 and 40 years of age participated in the study. Smooth syllable strings of the syllable /baep:/ were whispered and phonated at three different loudness levels (soft, medium, and loud) and three voice qualities (breathy, normal, and pressed). The voice qualities are associated with different adduction levels. This resulted in 18 treatment combinations (three adduction levels × three loudness levels × two sexes). A regression analysis was performed using a PROC MIXED procedure with SAS statistical software. Under similar production conditions, subglottal pressure was significantly lower in whisper than in phonation in 10 of 18 combinations, mean glottal airflow was significantly higher in whisper than in phonation in 13 of 18 combinations, and flow resistance was significantly lower in whisper than in phonation in 14 of 18 combinations, with the female subjects demonstrating these trends more frequently than the male subjects do. Of importance, in general, compared with phonation under similar production conditions, whisper is not always accompanied by lower subglottal pressure and higher airflows. Results from this study suggest that the typical finding of lower subglottal pressure, higher glottal airflow, and decreased flow resistance in whisper compared with phonation cannot be generalized to all individuals and depends on the "whisper type." The nine basic production conditions (three loudness levels and three adduction levels) resulted in data that may help explain the wide range of variation of whisper production reported in earlier studies.

Sensitivity of Source-Filter Interaction to Specific Vocal Tract Shapes.

A systematic variation of length and cross-sectional area of specific segments of the vocal tract (trachea to lips) was conducted computationally to quantify the effects of source-filter interaction. A one-dimensional Navier-Stokes (transmission line) solution was used to compute peak glottal airflow, maximum flow declination rate, and formant ripple on glottal flow for Level 1 (aero-acoustic) interactions. For Level 2 (tissue movement) interaction, peak glottal area, phonation threshold pressure, and deviation in fo were quantified. Results show that the ventricle, the false-fold glottis, the conus elasticus entry, and the laryngeal vestibule are the regions to which acoustic variables are most sensitive. Generally, any narrow section of the vocal tract increases the degree of interaction, both in terms of its length and its cross-sectional area. The closer the narrow section is to the vocal folds, the greater the effect.

Formant Tuning and Feedback in the Male Passaggio

It has been suggested that traversing the male (secondo) passaggio requires two important adjustments. When singing up the scale, first of all, the second harmonic (H2) needs to pass over the first formant (F1). After that, the timbre of the voice takes on a different, slightly "darker" quality. This is the pitch where, in singers' jargon, the voice reaches secondo passaggio. Above secondo passaggio, in the optimal arrangement, the second formant (F2) is tuned close to one of the higher harmonics, or, sometimes alternatively, the singer's formant cluster induces a dominant resonance in the approximate range of 2.4-3.4 kHz. These two adjustments together produce the typical sound of the classical male upper voice. In this study, we have investigated the choices individual singers make while negotiating the passaggio and the effect of feedback from the vocal tract to the voice source during this maneuver. Electroglottograph (EGG) and microphone signals were recorded of nine male singers (five tenors and four baritones) using VoceVista. Inverse filtering was performed on the microphone signals, using the Sopran/DeCap application, to reveal the shape of the glottal airflow pulses.

Immediate Effects of the Vocal Function Exercises Semi-Occluded Mouth Posture on Glottal Airflow Parameters: A Preliminary Study

The study aimed to quantify immediate alterations in the airflow glottogram between the Vocal Function Exercises semi-occluded mouth posture (/ol/ with lip buzz) and the sustained vowel /o/ in individuals with normal voices, and to determine if noted changes were in agreement with established semi-occluded vocal tract aerodynamic theory. Based on semi-occluded vocal tract aerodynamic theory, we hypothesized the following immediate changes in the flow glottogram during the /ol-buzz/ condition: a greater open quotient, a greater skewing quotient, a greater maximum flow declination rate, increased average airflow, decreased peak airflow, and increased minimum airflow. A cohort of eight men with normal voices produced the sustained vowel /o/ and the Vocal Function Exercises semi-occluded mouth posture (/ol-buzz/). Flow glottograms for both conditions were obtained from the inverse-filtered oral airflow signal via a circumferentially vented pneumotachograph mask. Data revealed that open quotient and minimum airflow rates increased significantly between conditions. All other measures trended in the directions predicted by aerodynamic theory, but were not statistically significant. The Vocal Function Exercises semi-occluded mouth posture appeared to provide an effective vocal tract semi-occlusion that immediately altered the flow glottogram in accordance with predictions made by computer-modeled aerodynamic theory.

Simulations of three-dimensional, self-oscillating vocal fold replicas with liquid-filled cavities

Synthetic, self-oscillating vocal fold replicas are used in bioreactors to study the response of injected cells to phono-mimetic vibrations. In this type of replica, cells are contained within a cylindrically shaped cavity that runs anterioposteriorly and that is located near the replica surface. During vocal fold replica flow-induced vibration, the cavity deforms, thereby subjecting the cells to a periodically varying stress field. The characteristics of this stress field are unknown, and experimental determination is not presently feasible. Therefore, in this research, numerical simulations of these self-oscillating, cell-containing synthetic replicas are studied. A three-dimensional vocal fold model containing a liquid-filled cavity, developed using the commercial software package ADINA, is described. The effects of glottal airflow are modeled using the mechanical energy equation to simulate the pressure distribution along the replica airway surface. The liquid-filled cavity is modeled through a fully ...

Nonstimulated rabbit phonation model: Cricothyroid approximation.

To describe a nonstimulated in vivo rabbit phonation model using an Isshiki type IV thyroplasty and uninterrupted humidified glottal airflow to produce sustained audible phonation. Prospective animal study. Six New Zealand white breeder rabbits underwent a surgical procedure involving an Isshiki type IV thyroplasty and continuous airflow delivered to the glottis. Phonatory parameters were examined using high-speed laryngeal imaging and acoustic and aerodynamic analysis. Following the procedure, airflow was discontinued, and sutures remained in place to maintain the phonatory glottal configuration for microimaging using a 9.4 Tesla imaging system. High-speed laryngeal imaging revealed sustained vocal fold oscillation throughout the experimental procedure. Analysis of acoustic signals revealed a mean vocal intensity of 61 dB and fundamental frequency of 590 Hz. Aerodynamic analysis revealed a mean airflow rate of 85.91 mL/s and subglottal pressure of 9 cm H2 O. Following the procedure, microimaging revealed that the in vivo phonatory glottal configuration was maintained, providing consistency between the experimental and postexperimental laryngeal geometry. The latter provides a significant milestone that is necessary for geometric reconstruction and to allow for validation of computational simulations against the in vivo rabbit preparation. We demonstrate a nonstimulated in vivo phonation preparation using an Isshiki type IV thyroplasty and continuous humidified glottal airflow in a rabbit animal model. This preparation elicits sustained vocal fold vibration and phonatory measures that are consistent with our laboratory's prior work using direct neuromuscular stimulation for evoked phonation. N/A. Laryngoscope, 126:1589-1594, 2016.

Subject-Specific Computational Modeling of Evoked Rabbit Phonation.

When developing high-fidelity computational model of vocal fold vibration for voice production of individuals, one would run into typical issues of unknown model parameters and model validation of individual-specific characteristics of phonation. In the current study, the evoked rabbit phonation is adopted to explore some of these issues. In particular, the mechanical properties of the rabbit's vocal fold tissue are unknown for individual subjects. In the model, we couple a 3D vocal fold model that is based on the magnetic resonance (MR) scan of the rabbit larynx and a simple one-dimensional (1D) model for the glottal airflow to perform fast simulations of the vocal fold dynamics. This hybrid three-dimensional (3D)/1D model is then used along with the experimental measurement of each individual subject for determination of the vocal fold properties. The vibration frequency and deformation amplitude from the final model are matched reasonably well for individual subjects. The modeling and validation approaches adopted here could be useful for future development of subject-specific computational models of vocal fold vibration.

Respiratory Laryngeal Coordination in Airflow Conservation and Reduction of Respiratory Effort of Phonation

This study evaluates the need of airflow conservation and the effect of glottal resistance on respiratory effort of phonation under different phonation conditions. A computational model of the pressure-volume-flow relationship of the respiratory system is developed. Simulations show that increasing the glottal resistance reduces the glottal airflow and allows phonation to be sustained for a longer breath group duration. For a given breath group duration, the reduced airflow also allows phonation to be sustained within a narrow range of lung volumes, thus lowering the overall respiratory effort. This study shows that for breath group durations and subglottal pressures typical of normal conversational speech, airflow conservation or maintaining "effortless" respiratory support does not provide a stricter requirement on the glottal resistance than that required for initiating phonation. However, the need for airflow conservation and respiratory effort reduction becomes relevant when the target subglottal pressure and breath group duration increase as in prolonged speech or singing or in conditions of weakened pulmonary function. In those conditions, the glottal resistance is expected to increase proportionally with increasing subglottal pressure to conserve airflow consumption and reduce respiratory effort.

Using Ambulatory Voice Monitoring to Investigate Common Voice Disorders: Research Update.

Many common voice disorders are chronic or recurring conditions that are likely to result from inefficient and/or abusive patterns of vocal behavior, referred to as vocal hyperfunction. The clinical management of hyperfunctional voice disorders would be greatly enhanced by the ability to monitor and quantify detrimental vocal behaviors during an individual’s activities of daily life. This paper provides an update on ongoing work that uses a miniature accelerometer on the neck surface below the larynx to collect a large set of ambulatory data on patients with hyperfunctional voice disorders (before and after treatment) and matched-control subjects. Three types of analysis approaches are being employed in an effort to identify the best set of measures for differentiating among hyperfunctional and normal patterns of vocal behavior: (1) ambulatory measures of voice use that include vocal dose and voice quality correlates, (2) aerodynamic measures based on glottal airflow estimates extracted from the accelerometer signal using subject-specific vocal system models, and (3) classification based on machine learning and pattern recognition approaches that have been used successfully in analyzing long-term recordings of other physiological signals. Preliminary results demonstrate the potential for ambulatory voice monitoring to improve the diagnosis and treatment of common hyperfunctional voice disorders.

Analysis of Measured and Simulated Supraglottal Acoustic Waves

To date, although much attention has been paid to the estimation and modeling of the voice source (ie, the glottal airflow volume velocity), the measurement and characterization of the supraglottal pressure wave have been much less studied. Some previous results have unveiled that the supraglottal pressure wave has some spectral resonances similar to those of the voice pressure wave. This makes the supraglottal wave partially intelligible. Although the explanation for such effect seems to be clearly related to the reflected pressure wave traveling upstream along the vocal tract, the influence that nonlinear source-filter interaction has on it is not as clear. This article provides an insight into this issue by comparing the acoustic analyses of measured and simulated supraglottal and voice waves. Simulations have been performed using a high-dimensional discrete vocal fold model. Results of such comparative analysis indicate that spectral resonances in the supraglottal wave are mainly caused by the regressive pressure wave that travels upstream along the vocal tract and not by source-tract interaction. On the contrary and according to simulation results, source-tract interaction has a role in the loss of intelligibility that happens in the supraglottal wave with respect to the voice wave. This loss of intelligibility mainly corresponds to spectral differences for frequencies above 1500Hz.