Acoustics and aerodynamic effects following glottal and infraglottal medialization in an excised larynx model.

OBJECTIVE: This study aimed to investigate the impact of the implant's vertical location during Type 1 Thyroplasty (T1T) on acoustics and glottal aerodynamics using excised canine larynx model, providing insights into the optimal technique for treating unilateral vocal fold paralysis (UVFP). METHODS: Measurements were conducted in six excised canine larynges using Silastic implants. Two implant locations, glottal and infraglottal, were tested for each larynx at low and high subglottal pressure levels. Acoustic and intraglottal flow velocity field measurements were taken to assess vocal efficiency (VE), cepstral peak prominence (CPP), and the development of intraglottal vortices. RESULTS: The results indicated that the implant's vertical location significantly influenced vocal efficiency (p = 0.045), with the infraglottal implant generally yielding higher VE values. The effect on CPP was not statistically significant (p = 0.234). Intraglottal velocity field measurements demonstrated larger glottal divergence angles and stronger vortices with the infraglottal implant. CONCLUSION: The findings suggest that medializing the paralyzed fold at the infraglottal level rather than the glottal level can lead to improved vocal efficiency. The observed larger divergence angles and stronger intraglottal vortices with infraglottal medialization may enhance voice outcomes in UVFP patients. These findings have important implications for optimizing T1T procedures and improving voice quality in individuals with UVFP. Further research is warranted to validate these results in clinical settings.

Computational Modeling of Voice Production Using Excised Canine Larynx.

A combined experimental-numerical work was conducted to comprehensively validate a subject-specific continuum model of voice production in larynx using excised canine laryngeal experiments. The computational model is a coupling of the Navier-Stokes equations for glottal flow dynamics and a finite element model of vocal fold dynamics. The numerical simulations employed a cover-body vocal fold structure with the geometry reconstructed from magnetic resonance imaging scans and the material properties determined through an optimization-based inverse process of experimental indentation measurement. The results showed that the simulations predicted key features of the dynamics observed in the experiments, including the skewing of the glottal flow waveform, mucosal wave propagation, continuous increase of the divergent angle and intraglottal swirl strength during glottal closing, and flow recirculation between glottal jet and vocal fold. The simulations also predicted the increase of the divergent angle, glottal jet speed, and intraglottal flow swirl strength with the subglottal pressure, same as in the experiments. Quantitatively, the simulations over-predicted the frequency and jet speed and under-predicted the flow rate and divergent angle for the larynx under study. The limitations of the model and their implications were discussed.

Open Versus Endoscopic Surgery of Zenker's Diverticula: A Systematic Review and Meta-analysis.

Most Zenker's diverticula (ZD) cohort studies are single-institution retrospective observational studies of recurrence rates. There is a gap in the literature regarding patient-reported outcomes after ZD surgery. This study was conducted to compare if open transcervical diverticulectomy (OD) is better than endoscopic laser diverticulectomy (ELD) or endoscopic stapler-assisted diverticulectomy (ESD). The study design is of systematic review and meta-analysis. The following databases were searched: SCOPUS, EMBASE, PubMed, and Word of Science through December 2017. The quality of the studies was evaluated using 22-item STROBE checklist with 3 independent physician reviewers. The Inter-rater reliability was calculated both as a percent and utilizing Cohen's Kappa. For the meta-analysis, Cohen's d for an effect size was calculated for all studies comparing dysphagia results before and after surgery. A total of 865 patients were treated across 11 selected publications, of which 106 patients were treated OD, 310 ELD, and 449 with an ESD approach. Patient-reported dysphagia outcomes were reported as Cohen's d (confidence interval): OD, ELD, and ESD were 1.31 (0.88, 1.74), 1.91 (1.62, 2.20), and 2.45 (2.04, 2.86), respectively. The pooled effect of all studies for dysphagia was 2.22 (1.85, 2.59) and regurgitation 2.20 (1.80, 2.59). We did not prove that OD has superior outcomes compared to ESD and ELD. Any method of surgical intervention yields a large effect (i.e., improvement in dysphagia and regurgitation) comparing patient-reported symptoms before and after surgery. Future research, currently underway, includes a prospective, multi-institutional study comparing standardized outcomes between treatments of ZD including symptom resolution, complications, and recurrences using validated measures to define long-term outcomes.Level of Evidence 3.

Comparison of glottal flow rate characteristics based on experimental and computational data.

In a recent computational model, Farahani and Zhang [J. Acoust. Soc. Am. 136, EL369-EL375 (2014)] concluded that intraglottal vortices did not affect the closing mechanism of the folds. In order to determine the validity of any model that addresses the issue of vortex significance, it is important that the results of the computational model are comparable to experimental results. The results of Farahani and Zhang's model are inconsistent with data published for experimental models, which may challenge the validity of their conclusions.

Intraglottal velocity and pressure measurements in a hemilarynx model.

Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model.

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.

An Ex-vivo Model Examining Acoustics and Aerodynamic Effects Following Medialization With and Without Arytenoid Adduction.

OBJECTIVES/HYPOTHESIS: Quantify differences in acoustics and intraglottal flow fields between Thyroplasty Type 1 (TT1) with and without arytenoid adduction (AA) using excised canine larynx model. STUDY DESIGN: Basic science experiments using excised larynges. METHODS: Surgical procedures were implemented in eight excised canine larynges. Acoustics and intraglottal flow measurements were taken at low and high subglottal pressures in each experimental setup. RESULTS: In all larynges, vocal efficiency (VE) and cepstrum peak prominence (CPP) were higher, and the mean phonatory flow rate was lower in TT1 with AA than without AA. The glottal asymmetry is reduced with AA and promotes the formation of stronger vortices in the glottal flow during the closing phase of the vibrating folds. CONCLUSIONS: Findings suggest a clear acoustic and aerodynamic benefit to the addition of AA when performing TT1. It shows significant improvement in CPP, translating to decreased breathiness and dysphonia and increased VE, leading to easier and more sustainable phonation. Stronger intraglottal vortices are known to be correlated with the loudness of voice produced by phonation. LEVEL OF EVIDENCE: N/A Laryngoscope, 133:621-627, 2023.

Acoustic Screening of the "Wet voice": Proof of Concept in an ex vivo Canine Laryngeal Model.

BACKGROUND: Current protocols for bedside swallow evaluation have high rates of false negative results. Though experts are not consistently able to screen for aspiration risk by assessing vocal quality, there is emerging evidence that vocal acoustic parameters are significantly different in patients at risk of aspiration. Herein, we aimed to determine whether the presence of material on the vocal folds in an excised canine laryngeal model may have an impact on acoustic and aerodynamic measures. METHODS: Two ex vivo canine larynges were tested. Three liquids of different viscosities (1:100 diluted glycerin, pure glycerin, and honey-thick Varibar) were placed on the vocal folds at a constant volume. Acoustic and aerodynamic measures were obtained in both adducted and abducted vocal fold configurations. Intraglottal high-speed imaging was used to approximate the maximum divergence angle of the larynges in the studied conditions and examine its relationship to vocal efficiency (VE) and acoustic measures. RESULTS: In glottic insufficiency conditions only, we found that several acoustic parameters could predict the presence of material on the vocal folds. Based on the combination of the aerodynamic and acoustic data, we found that decreased spectral energy in the higher harmonics was associated with decreased VE in the presence of material on the vocal folds and/or glottic insufficiency. CONCLUSION: Decreased spectral energy in the higher harmonics of the voice was found to be a potential biomarker of swallowing dysfunction, as it correlates with decreased vocal efficiency due to material on the vocal folds and/or glottic insufficiency, both of which are known risk factors for aspiration. LEVEL OF EVIDENCE: NA Laryngoscope, 133:2517-2524, 2023.

Killian Jamieson Diverticulum, the Great Mimicker: A Case Series and Contemporary Review.

OBJECTIVE: To assess barium esophagram (BAS) as a diagnostic marker for patients with Killian Jamieson diverticula (KJD). METHODS: Prospective, multicenter cohort study of individuals enrolled in the Prospective OUtcomes of Cricopharyngeus Hypertonicity (POUCH) Collaborative. Patient demographics, comorbidities, radiographic imaging reports, laryngoscopy findings, patient-reported outcome measures (PROM), and operative reporting were abstracted from a REDCap database and summarized using means, medians, percentages, frequencies. Paired t-tests and Wilcoxon Signed Rank test were used to test pre- to post-operative differences in RSI, EAT-10, and VHI-10 scores. Diagnostic test evaluation including sensitivity, specificity, positive, and negative predictive value with 95% confidence intervals were calculated comparing BAS findings to operative report. RESULTS: A total of 287 persons were enrolled; 13 (4%) patients were identified with confirmed KJD on operative reports. 100% underwent open transcervical excision. BAS has a 46.2% (95% confidence interval [CI]: 23.2, 70.9) sensitivity and 97.8% (95% CI: 95.3, 99.0) specificity in detecting a KJD and 50% (95% CI: 25.4, 74.6) positive predictive value but 97.4% (95%CI: 94.8, 98.7) negative predictive value. Preoperatively, patients reported mean (SD) RSI and EAT-10 of 19.4 (9) and 8.3 (7.5) accordingly. Postoperatively, patients reported mean (SD) RSI and EAT-10 as 5.4 (6.2) and 2.3 (3.3). Both changes in RSI and EAT-10 were statistically significant (p = 0.008, p = 0.03). CONCLUSION: KJD are rare and represent <5% of hypopharyngeal diverticula undergoing surgical intervention. Open transcervical surgery significantly improves symptoms of dysphagia. BAS has high specificity but low sensitivity in detecting KJD. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:2110-2115, 2023.

Cricopharyngeus Muscle Dysfunction and Hypopharyngeal Diverticula (e.g., Zenker): A Multicenter Study.

OBJECTIVE: To describe demographics and imaging and compare findings and symptoms at presentation in a large cohort of persons with cricopharyngeus muscle dysfunction (CPMD) with and without hypopharyngeal diverticula. METHODOLOGY: Prospective, multicenter cohort study of all individuals enrolled in the Prospective OUtcomes of Cricopharyngeal Hypertonicity (POUCH) Collaborative. Patient survey, comorbidities, radiography, laryngoscopy findings, and patient-reported outcome measures (e.g., Eating Assessment Tool [EAT-10]) data were abstracted from a REDCap database and summarized using means, medians, percentages, and frequencies. Diagnostic categories were compared using analysis of variance. RESULTS: A total of 250 persons were included. The mean age (standard deviation [SD]) of the cohort was 69.0 (11.2). Forty-two percent identified as female. Zenker diverticula (ZD) was diagnosed in 85.2%, 9.2% with CPMD without diverticula, 4.4% with a Killian Jamieson diverticula (KJD), and 1.2% traction-type diverticula. There were no differences between diagnostic categories in regard to age, gender, and duration of symptoms (p = 0.25, 0.19, 0.45). The mean (SD) EAT-10 score for each group was 17.1 (10.1) for ZD, 20.2 (9.3) for CPMD, and 10.3 (9.4) for KJD. Patients with isolated CPMD had significantly greater EAT-10 scores compared to the other diagnostic groups (p = 0.03). CONCLUSION: ZD is the most common, followed by CPMD without diverticula, KJD, and traction-type. Patients with isolated obstructing CPMD may be more symptomatic than persons with ZD or KJD. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:1349-1355, 2023.

Comparative Treatment Outcomes for Idiopathic Subglottic Stenosis: 5-Year Update.

The North American Airway Collaborative (NoAAC) previously published a 3-year multi-institutional prospective cohort study showing variation in treatment effectiveness between 3 primary surgical techniques for idiopathic subglottic stenosis (iSGS). In this report, we update these findings to include 5 years of data evaluating treatment effectiveness. Patients in the NoAAC cohort were re-enrolled for 2 additional years and followed using the prespecified published protocol. Consistent with prior data, prospective observation of 487 iSGS patients for 5 years showed treatment effectiveness differed by modality. Cricotracheal resection maintained the lowest rate of recurrent operation (5%), followed by endoscopic resection with adjuvant medical therapy (30%) and endoscopic dilation (50%). These data support the initial observations and continue to provide value to providers and patients navigating longitudinal decision-making. Level of evidence: 2-prospective cohort study.

Are Indoor Cycling Instructors Riding Their Way to Vocal Injury? Acute Effects of a Single Class on Measures of Voice Production.

OBJECTIVE/HYPOTHESIS: There is an increased need for vocal education programs in group fitness instructors due to the reported risk of phonotraumatic injury in this population. Most research has focused on aerobics class instructors with limited research detailing the vocal demand response of cycling instruction, specifically. We hypothesized that instruction of a single indoor cycling class would produce evidence of acute vocal fold edema manifested by worsening of acoustic and self-perceptual voice measures and changes in ratings of laryngeal appearance. STUDY DESIGN: Prospective Cohort study. METHODS: Acoustic and self-perceptual voice measures that were potentially sensitive to laryngeal edema were collected from ten cycling instructors (Mean age: 31 ± 6.14 years, 3M and 7F) before and after instruction of a typical 45-minute cycling class. Two laryngologists then rated pairs of laryngeal exams from five instructors (Mean age: 30 ± 6.22 years, 1M and 4F) on the measure of vocal fold edema using a 10-inch Visual Analogue Scale. Paired t-test comparisons were completed on normalized data to compare pre- and postinstruction. RESULTS: Majority of acoustic and self-perceptual measures significantly worsened following cycling instruction but the magnitude of change in these measures were small. In terms of laryngeal appearance, no measurable change in vocal fold edema was observed at both time points. CONCLUSION: The vocal demand response to a single cycling class may be insufficient to cause significant vocal fold edema in our cycling instructors. Future research is required to determine the effects of repeated cycling instruction.

Computational Modeling of Nasal Drug Delivery Using Different Intranasal Corticosteroid Sprays for the Treatment of Eustachian Tube Dysfunction.

Eustachian tube dysfunction (ETD) is a common otolaryngologic condition associated with decreased quality of life. The first-line treatment of ETD is intranasal corticosteroid sprays (INCS). Computational fluid dynamics (CFD) was used to study particle deposition on the Eustachian tube (ET) using two commercial INCS (Flonase and Sensimist). Simulations also considered the effects of nostril side, insertion depth, insertion angle, cone spray angle, inhaling rates, wall impingement treatment, and fluid film. Flonase and Sensimist produced different particle size distributions and sizes. Sensimist droplets are smaller, less sensitive to asymmetry in nostrils anatomy and variation in insertion angle, and therefore can reach the posterior nasopharynx more readily. Flonase produces larger particles with greater inertia. Its particles deposition is more sensitive to intrasubject variation in nasal anatomy and insertion angles. The particle deposition on the ET was sensitive to the wall impingement model. The deposition on the ET was insignificant with adherence only <0.15% but increased up to 1-4% when including additional outcomes rebound and splash effects when droplets impact with the wall. The dose redistribution with the fluid film is significant but plays a secondary effect on the ET deposition. Flonase aligned parallel with the hard palate produced 4% deposition efficiency on the ET, but this decreased <0.14% at the higher insertion angle. INCS with larger droplet sizes with a small insertion angle may be more effective at targeting droplet deposition on the ET opening.

Surgery and Adjuvant Therapy Improve Derkay Scores in Adult and Pediatric Respiratory Papillomatosis.

OBJECTIVES/HYPOTHESIS: Comparing Derkay anatomical score at time of procedure, disease characteristics, and mean treatment interval among adult and pediatric patients with recurrent respiratory papillomatosis (RRP). STUDY DESIGN: Restrospective study. METHODS: Retrospective review of juvenile-onset (JO) and adult-onset (AO) RRP patients treated longitudinally at pediatric and adult institutions from 1999 to 2019. Patients were included if they had a tissue diagnosis of papilloma and had at least a 12-month follow-up. RESULTS: One hundred and twelve patients met inclusion criteria (68 JO-RRP and 44 AO-RRP). All patients were stratified into either potassium titanyl phosphate (KTP) (n = 42), CO2 (n = 21), or microdebrider (n = 49) treatment groups. The Derkay score improved between first and last procedure in the KTP group (mean difference, 3.5; P < .001), CO2 group (mean difference, 4.4; P < .001), and microdebrider group (mean difference, 4.1; P < .001), but overall improvement did not differ across groups (P = .73). Baseline mean to last mean Derkay score improved for nine patients during bevacizumab treatments (mean difference, 3.0; P = .01) but did not improve for these same patients during an interval prior to receiving bevacizumab treatments. Baseline mean to last mean Derkay score improved for 19 patients during cidofovir treatments (mean difference, 3.84; P < .001) but did not improve for these same patients during the interval prior to receiving cidofovir treatments. The AO-RRP population had more patients with dysplasia (50%) compared to JO-RRP population (10%) (P < .001). CONCLUSION: Various surgical modalities appear to be equally effective treatments for RRP. Adult and pediatric patients have decreased recurrent disease burden when receiving bevacizumab or cidofovir. AO-RRP patients have more concomitant dysplasia. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:2420-2426, 2022.

Fluid-Structure Interaction Analysis of Aerodynamic and Elasticity Forces During Vocal Fold Vibration.

The effect of the intraglottal vortices on the glottal flow waveform was explored using flow-structure-interaction (FSI) modeling. These vortices form near the superior aspect of the vocal folds during the closing phase of the folds' vibration. The geometry of the vocal fold was based on the well-known M5 model. The model did not include a vocal tract to remove its inertance effect on the glottal flow. Material properties for the cover and body layers of the folds were set using curve fit to experimental data of tissue elasticity. A commercially available FSI solver was used to perform simulations at low and high values of subglottal input pressure. Validation of the FSI results showed a good agreement for the glottal flow and the vocal fold displacement data with measurements taken in the excised canine larynx model. The simulations result further support the hypothesis that intraglottal vortices can affect the glottal flow waveform, specifically its maximum flow declination rate (MFDR). It showed that MFDR occurs at the same phase when the highest intraglottal vortical strength and the negative pressure occur. It also showed that when MFDR occurs, the magnitude of the aerodynamic force acting on the glottal wall is greater than the elastic recoil force predicted in the tissue. These findings are significant because nearly all theoretical and computational models that study the vocal fold vibrations mechanism do not consider the intraglottal negative pressure caused by the vortices as an additional closing force acting on the folds.

Montgomery's Aperture: An External Anatomic Landmark for Surgical Identification of the Anterior Commissure.

OBJECTIVES: This study evaluates the consistency of palpable identification of an external landmark for the anterior commissure (AC), termed Montgomery's aperture (MA), in cadaveric and surgical settings. METHODS: Part 1: In human cadaveric larynges, palpation of the external laryngeal framework was used to identify MA by three blinded otolaryngologists. The vertical height (VH) of the thyroid cartilage and distance from MA to the inferior border of the thyroid cartilage were measured, larynges were bisected, and the AC was identified and measured. Surface anatomy was demonstrated visually using 3D imaging. Part 2: Retrospectively collected case series used palpation of MA in thyroplasty type 1 (TT1) and compared the result to ½ VH. RESULTS: Part 1: MA was identified in seven cadavers by three surgeons. In four of seven MA was palpated at the location of AC. The average difference between the AC and MA was -0.95 ± 0.96 mm. The average difference between AC and ½VH was 0.08 ± 0.72 mm. Part 2: In 49 patients (57% females) who underwent TT1, MA correlated within ½VH in 67% of cases. MA was inferior to ½VH in 27% of cases, on average 1.08 mm ± 0.51 mm below ½VH. MA was not palpable in 6% (3 of 49) of patients. CONCLUSION: We define the MA as the external indentation or flattening of the thyroid cartilage located within 1 millimeter inferior or at ½ VH of the thyroid cartilage. MA is a reliable, reproducible, palpable landmark for the anterior commissure. It serves as an important landmark that can be used in laryngoplastic surgery in which accurate prediction of the glottis is important.

Surgical Treatment of Acquired Velopharyngeal Insufficiency in Adults With Dysphagia and Dysphonia.

OBJECTIVES: Velopharyngeal insufficiency (VPI) is a form of velopharyngeal dysfunction caused by abnormal or insufficient anatomy. This process is known to be associated with dysphagia and dysphonia but surgical interventions for these complex patients have not been well studied. The current study characterized a small cohort of adult patients with acquired VPI, dysphonia, and dysphagia, as well as associated surgical interventions. METHODS: A retrospective descriptive case series of 22 (N = 22) adult patients over a 6-year period with acquired VPI and varying degrees of dysphagia and dysphonia was described from a multi-disciplinary voice and swallowing clinic. Perceptual assessment, nasopharyngoscopy, fluoroscopic swallowing assessment, and patient reported outcomes were reviewed to characterize the cohort. RESULTS: VPI etiologies included: stroke (n = 4), head and neck cancer (n = 5), brainstem lesions (n = 5), trauma (n = 5), and other/unknown (n = 3). All 22 patients underwent nasopharyngoscopy and were categorized as having unilateral (n = 13), central (n = 4), or no (n = 5) velopharyngeal deficits. Seventeen patients (77.2%) underwent modified barium swallow studies, revealing that soft palate elevation scored least impaired among patients with no VPI, and most impaired among patients with unilateral VPI deficits. All 22 patients underwent some form of surgical intervention for VPI, with 14 (63.6%) of those patients requiring additional surgical revision. CONCLUSION: This series is one of the first to the authors' knowledge to characterize a cohort of individuals with VPI, dysphagia, and dysphonia and associated surgical interventions.

Medial Surface Dynamics as a Function of Subglottal Pressure in a Canine Larynx Model.

During vocal fold vibration, there may be a mucosal wave in the superior-inferior (vertical) direction, resulting in a convergent shape during opening and a divergent shape during closing. Most of our understanding of the converging/diverging shape of the glottis has come from studies in a hemilarynx model. Previous work has shown that vibratory patterns in the full excised larynx are different than the hemilarynx. This study characterized the dynamics of the medial glottal wall geometry during vibrations in the full excised canine larynx model. Using particle image velocimetry, the intraglottal geometry was measured at the midmembranous coronal plane in an excised canine larynx model. Measurements of the glottal area were taken simultaneously using high-speed imaging. The results show that skewing of the glottal area waveform occurs without the presence of a vocal tract and that the phase-lag of the superior edge relative to the inferior edge is smaller than reported and depends on the subglottal pressure. In addition, it shows that the glottal divergence angle during closing is proportional to the magnitude of the acoustic intensity and the intraglottal negative pressure. This preliminary data suggests that more studies are needed to determine the important mechanisms determining the relationship between intraglottal flow, intraglottal geometry, and acoustics.

Effects of False Vocal Folds on Intraglottal Velocity Fields.

Previous models have theorized that, during phonation, skewing of the glottal waveform (which is correlated with acoustic intensity) occurred because of inertance of the vocal tract. Later, we reported that skewing of the flow rate waveform can occur without the presence of a vocal tract in an excised canine larynx. We hypothesized that in the absence of a vocal tract, the skewing formed when dynamic pressures acted on the glottal wall during the closing phase; such pressures were greatly affected by formation of intraglottal vortices. In this study, we aim to identify how changes in false vocal folds constriction can affect the acoustics and intraglottal flow dynamics. The intraglottal flow measurements were made using particle image velocimetry in an excised canine larynx where a vocal tract model was placed above the larynx and the constriction between the false vocal folds was varied. Our results show that for similar values of subglottal pressures, the skewing of the glottal waveform, strength of the intraglottal vortices, and acoustic energy increased as the constriction between the false vocal folds was increased. These preliminary findings suggest that acoustic intensity during phonation can be increased by the addition of a vocal tract with false fold constriction.

Quantification of the Intraglottal Pressure Induced by Flow Separation Vortices Using Large Eddy Simulation.

The greatest rate of change in the glottal flow rate during phonation is a rapid decrease that occurs during the latter part of the glottal closing. Previous works showed that intraglottal flow separation vortices form in a divergent glottis, produce negative gauge pressures (below atmospheric) during closing. It is hypothesized here that flow separation vortices contribute to the rapid closing mechanism of the true vocal folds during phonation. Four idealized static models (M5) of the human larynx were investigated using large eddy simulation: 2 models featured parallel folds that did not enable flow separation in the glottis and 2 models involved a divergent glottis. The influence of the ventricular gap (narrow/wide) is evaluated. An unsteady pressure inlet representing a voicing cycle was applied to the sub-glottal region to mimic the time-varying glottal flow. Intraglottal vortex structures formed downstream of the separation point in a divergent glottis. Their existence caused a higher closing force that was applied onto the vocal folds. A narrow ventricular gap strengthens this effect. Strength of the intraglottal vortices increased with the maximum flow declination rate. Therefore, a more divergent shape of the glottis during glottal closing will be one of the main contributors to the voice quality.