Mucosal wave measurement and visualization techniques

Ultrasound applicability in Speech Language Pathology and Audiology

PURPOSE: To present recent studies that used the ultrasound in the fields of Speech Language Pathology and Audiology, which evidence possibilities of the applicability of this technique in different subareas. RESEARCH STRATEGY: A bibliographic research was carried out in the PubMed database, using the keywords "ultrasonic," "speech," "phonetics," "Speech, Language and Hearing Sciences," "voice," "deglutition," and "myofunctional therapy," comprising some areas of Speech Language Pathology and Audiology Sciences. The keywords "ultrasound," "ultrasonography," "swallow," "orofacial myofunctional therapy," and "orofacial myology" were also used in the search. SELECTION CRITERIA: Studies in humans from the past 5 years were selected. In the preselection, duplicated studies, articles not fully available, and those that did not present direct relation between ultrasound and Speech Language Pathology and Audiology Sciences were discarded. DATA ANALYSIS: The data were analyzed descriptively and classified subareas of Speech Language Pathology and Audiology Sciences. The following items were considered: purposes, participants, procedures, and results. RESULTS: We selected 12 articles for ultrasound versus speech/phonetics subarea, 5 for ultrasound versus voice, 1 for ultrasound versus muscles of mastication, and 10 for ultrasound versus swallow. Studies relating "ultrasound" and "Speech Language Pathology and Audiology Sciences" in the past 5 years were not found. CONCLUSION: Different studies on the use of ultrasound in Speech Language Pathology and Audiology Sciences were found. Each of them, according to its purpose, confirms new possibilities of the use of this instrument in the several subareas, aiming at a more accurate diagnosis and new evaluative and therapeutic possibilities.

High-speed video or video stroboscopy in adolescents: which sheds more light?

OBJECTIVE

The primary objective of this study was to compare the utility of high-speed video (HSV) to videostroboscopy (VS) in the assessment of adolescents with normal and abnormal larynges. A secondary objective was to evaluate the ease of assessment of adolescents with HSV.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary academic health care center.

SUBJECTS AND METHODS

This study involved a retrospective review of recordings of 7 adolescents assessed with both HSV and VS. The 14 recordings were randomized and presented to 4 groups of blinded evaluators: 2 fellowship-trained laryngologists, 2 speech language pathologists (SLP) with multiyear experience working in a voice clinic, 2 pediatric otolaryngologists, and 2 otolaryngology residents. Raters were asked to evaluate the videos using a standardized scoring tool. Raters also completed a questionnaire assessing their opinion of the HSV and VS recordings.

RESULTS

Evaluators required more time to complete their assessment of VS recordings (2.95 min ± 2.41 min) than HSV recordings (2.31 min ± 1.92 min) (P = .004). There was no difference in ease of evaluation (P = .878) or diagnostic accuracy within evaluator groups by recording modality (P = .5). The overall agreement between VS and HSV was moderate (kappa [SE] = 0.446 [0.029]). The debrief questionnaire revealed that 5 of 8 (62.5%) preferred VS to HSV.

CONCLUSION

This is the first comparative study between HSV and VS in patients under 18 years of age. HSV permitted faster evaluation than VS, but there was no difference in diagnostic accuracy between the 2 modalities. The evaluators preferred VS to HSV.

Quantitative analysis of digital videokymography: a preliminary study on age- and gender-related difference of vocal fold vibration in normal speakers

INTRODUCTION

Kymography is an effective method for assessing temporal patterns of vocal fold vibrations. Because kymographic data for a number of normal speakers based on high-speed digital imaging (HSDI) were limited in the literature, this prospective study was conducted to provide normative kymographic HSDI data and clarify gender- and age-related normal variations.

METHODS

Vocally healthy adults were divided into young (≤35 years) and elderly groups (≥65 years). Kymograms were recomposed from HSDI data at the midglottal level, and kymographic parameters were analyzed quantitatively. Then gender- and age-related differences were evaluated.

RESULTS

A total of 26 young subjects (9 men and 17 women, mean age: 27 years) and 20 elderly subjects (8 men and 12 women, mean age: 73 years) were investigated. Obtained data generally matched the values in the literature. Slight asymmetry was seen in all groups, with the elderly subjects having more evident asymmetry than the young subjects. Most of the kymographic parameters showed a negative correlation with fundamental frequency (F0), whereas the open quotient displayed a positive correlation with F0. There were significant intergroup differences in F0, amplitude and lateral peak at a speaking F0.

CONCLUSIONS

The present quantitative findings generally matched the qualitative kymographic data reported in the literature. When judging whether a vibratory pattern is normal or pathological, both gender and age should be taken into account, because gender- and age-related variations of symmetry, F0, and phase were frequently observed in the present study.

Spatiotemporal analysis of high-speed videolaryngoscopic imaging of organic pathologies in males

PURPOSE

The aim of this study was to identify parameters that would differentiate healthy from pathological organic-based vocal fold vibrations to emphasize clinical usefulness of high-speed imaging.

METHOD

Fifty-five men (M age = 36 years, SD = 20 years) were examined and separated into 4 groups: 1 healthy (26 individuals) and 3 pathological (10 individuals with contact granuloma, 12 with polyps, and 7 with cysts). Vocal fold vibrations were recorded using a high-speed camera during sustained phonation. Twenty objective glottal area waveform and 24 phonovibrogram parameters representing spatiotemporal characteristics were analyzed. Statistical group comparisons were performed to document spatiotemporal changes for organic lesions that cannot be determined visually. To look for specific pattern profiles within organic lesions, the authors performed linear discriminant analysis.

RESULTS

Thirteen parameters showed significant differences between the healthy group and at least 1 pathological group. The differences occurred more in temporal than in spatial parameters. Contact granuloma showed the fewest statistical differences (3 parameters), followed by cysts (9 parameters), and polyps (10 parameters). Linear discriminant analysis achieved accuracy performance of 76% (all groups separated) and 82% (healthy vs. pathological).

CONCLUSION

The results suggest that for males, the differences between healthy voices and organic voice disorders may be more pronounced within temporal characteristics that cannot be visually detected without high-speed imaging.

Acoustic characteristics of different target vowels during the laryngeal telescopy

OBJECTIVE

The aim of this study was to investigate the acoustic characteristics of target vowels phonated in normal voice persons while performing laryngeal telescopy. The acoustic characteristics are compared to show the extent of possible difference to speculate their impact on phonation function.

METHODS

Thirty-four male subjects aged 20-39 years with normal voice were included in this study. The target vowels were /i/ and /ɛ/. Recording of voice samples was done under natural phonation and during laryngeal telescopy. The acoustic analysis included the parameters of fundamental frequency, jitter, shimmer and noise-to-harmonic ratio.

RESULTS

The sound of a target vowel /ɛ/ was perceived identical in more than 90% of the subjects by the examiner and speech language pathologist during the telescopy. Both /i/ and /ɛ/ sounds showed significant difference when compared with the results under natural phonation. There was no significant difference between /i/ and /ɛ/ during the telescopy.

CONCLUSION

The present study showed that change in target vowels during laryngeal telescopy makes no significant difference in the acoustic characteristics. The results may lead to the speculation that the phonation mechanism was not affected significantly by different vowels during the telescopy. This study may suggest that in the principle of comfortable phonation, introduction of the target vowels /i/ and /ɛ/ is practical.

Investigating the three-dimensional flow separation induced by a model vocal fold polyp

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements.

Non-invasive in vivo measurement of the shear modulus of human vocal fold tissue

Voice is the essential part of singing and speech communication. Voice disorders significantly affect the quality of life. The viscoelastic mechanical properties of the vocal fold mucosa determine the characteristics of the vocal folds oscillations, and thereby voice quality. In the present study, a non-invasive method was developed to determine the shear modulus of human vocal fold tissue in vivo via measurements of the mucosal wave propagation speed during phonation. Images of four human subjects' vocal folds were captured using high speed digital imaging (HSDI) and magnetic resonance imaging (MRI) for different phonation pitches, specifically fundamental frequencies between 110 and 440 Hz. The MRI images were used to obtain the morphometric dimensions of each subject's vocal folds in order to determine the pixel size in the high-speed images. The mucosal wave propagation speed was determined for each subject and at each pitch value using an automated image processing algorithm. The transverse shear modulus of the vocal fold mucosa was then calculated from a surface (Rayleigh) wave propagation dispersion equation using the measured wave speeds. It was found that the mucosal wave propagation speed and therefore the shear modulus of the vocal fold tissue were generally greater at higher pitches. The results were in good agreement with those from other studies obtained via in vitro measurements, thereby supporting the validity of the proposed measurement method. This method offers the potential for in vivo clinical assessments of vocal folds viscoelasticity from HSDI.

AERODYNAMIC SOUND OF A BODY IN ARBITRARY, DEFORMABLE MOTION, WITH APPLICATION TO PHONATION

The method of tailored Green's functions advocated by Doak (Proceedings of the Royal Society A254 (1960) 129 - 145.) for the solution of aeroacoustic problems is used to analyse the contribution of the mucosal wave to self-sustained modulation of air flow through the glottis during the production of voiced speech. The amplitude and phase of the aerodynamic surface force that maintains vocal fold vibration are governed by flow separation from the region of minimum cross-sectional area of the glottis, which moves back and forth along its effective length accompanying the mucosal wave peak. The correct phasing is achieved by asymmetric motion of this peak during the opening and closing phases of the glottis. Limit cycle calculations using experimental data of Berry et al. (Journal of the Acoustical Society of America 110 (2001) 2539 - 2547.) obtained using an excised canine hemilarynx indicate that the mechanism is robust enough to sustain oscillations over a wide range of voicing conditions.

Kymographic imaging of laryngeal vibrations

PURPOSE OF REVIEW

Kymographic imaging is a modern method for displaying and evaluating vibratory behaviour of the vocal folds which is crucial for voice production. This review summarizes the state of the art of this method, and focuses on the progress in this area within the last 5 years.

RECENT FINDINGS

Videokymography, using a special videocamera, offers high-speed (video)kymographic images in real time, which is advantageous in daily clinical practice. Two other methods use software to create kymograms retrospectively: digital kymography processes high-speed videolaryngoscopic recordings and offers numerous research possibilities, whereas strobovideokymography processes videostroboscopic recordings, and its use is limited to regular vibration patterns. Current studies reveal that high-speed kymographic images allow more reliable visual evaluation of vibrations than by watching video recordings. Image analysis procedures have been advanced to quantify the vibration properties of the vocal folds. New information has been obtained on asymmetry, mucosal waves, irregularities, phonation onset, and nonlinear dynamic phenomena in voice disorders, as well as in singing.

SUMMARY

High-speed kymography visualizes vibratory features which are not simply observable via traditional methods. It shows large potential in better understanding the functional origin of hoarseness and unsteady phonatory states. Further research in this area is envisioned.

Current role of stroboscopy in laryngeal imaging

PURPOSE OF REVIEW

To summarize recent technological advancements and insight into the role of stroboscopy in laryngeal imaging.

RECENT FINDINGS

Although stroboscopic technology has not undergone major technological improvements, recent clarifications have been made to the application of stroboscopic principles to video-based laryngeal imaging. Also recent advances in coupling stroboscopy with high-definition video cameras provide higher spatial resolution of vocal fold vibratory function during phonation. Studies indicate that the interrater reliability of visual stroboscopic assessment varies depending on the laryngeal feature being rated and that only a subset of features may be needed to be representative of an entire assessment. High-speed videoendoscopy (HSV) judgments have been shown to be more sensitive than stroboscopy for evaluating vocal fold phase asymmetry, pointing to the future potential of complementing stroboscopy with alternative imaging modalities in hybrid systems. Laryngeal videostroboscopy alone continues to play a central role in clinical voice assessment. Even though HSV may provide more detailed information about phonatory function, its eventual clinical adoption will depend on how remaining practical, technical, and methodological challenges will be met.

SUMMARY

Laryngeal videostroboscopy continues to be the modality of choice for imaging vocal fold vibration, but technological advancements in HSV and associated research findings are driving increased interest in the clinical adoption of HSV to complement videostroboscopic assessment.

Visualizing collagen network within human and rhesus monkey vocal folds using polarized light microscopy

OBJECTIVES

Collagen fiber content and orientation affect the viscoelastic properties of the vocal folds, determining oscillation characteristics during speech and other vocalization. The investigation and reconstruction of the collagen network in vocal folds remains a challenge, because the collagen network requires at least micron-scale resolution. In this study, we used polarized light microscopy to investigate the distribution and alignment of collagen fibers within the vocal folds.

METHODS

Data were collected in sections of human and rhesus monkey (Macaca mulatta) vocal folds cut at 3 different angles and stained with picrosirius red.

RESULTS

Statistically significant differences were found between different section angles, implying that more than one section angle is required to capture the network's complexity. In the human vocal folds, the collagen fiber distribution continuously varied across the lamina propria (medial to lateral). Distinct differences in birefringence distribution were observed between the species. For the human vocal folds, high birefringence was observed near the thyroarytenoid muscle and near the epithelium. However, in the rhesus monkey vocal folds, high birefringence was observed near the epithelium, and lower birefringence was seen near the thyroarytenoid muscle.

CONCLUSIONS

The differences between the collagen networks in human and rhesus monkey vocal folds provide a morphological basis for differences in viscoelastic properties between species.

Decannulation and assessment of deglutition in the tracheostomized patient in non-neurocritical intensive care

With intensive care patients, decannulation and deglutition disorders are frequent reasons for otorhinolaryngological assessment. The objective of a tracheostomy is to maintain a patent airway. It does not necessarily prevent episodes of aspiration and may even favour them. When the cause that led to the tracheostomy resolves, a decannulation may be proposed. Deglutition is a complex act involving the coordinated interaction of several structures of the aerodigestive tract. Fibre-optic endoscopy and videofluoroscopy are 2 useful, complementary tools for the evaluation of patients with swallowing disorders. In managing these patients, a thorough knowledge of laryngeal and swallowing physiology, as well as of the different therapeutic alternatives, is required. Although it is not uncommon for swallowing disorders to coexist in tracheostomy patients, decannulation evaluation is not synonymous with deglutition assessment. A patient could be a candidate for decannulation and have a swallowing disorder, or a tracheostomy patient could swallow adequately. Knowing and understanding these concepts will lead to more efficient management and help to clarify communication between the intensive care physician and the otorhinolaryngologist. Ideally, a multidisciplinary team should be formed to evaluate and manage these patients.

Vocal fold vibration measurements using laser Doppler vibrometry

The objective of this study was to measure the velocity of the superior surface of human vocal folds during phonation using laser Doppler vibrometry (LDV). A custom-made endoscopic laser beam deflection unit was designed and fabricated. An in vivo clinical experimental procedure was developed to simultaneously collect LDV velocity and video from videolaryngoscopy. The velocity along the direction of the laser beam, i.e., the inferior-superior direction, was captured. The velocity was synchronous with electroglottograph and sound level meter data. The vibration energy of the vocal folds was determined to be significant up to a frequency of 3 kHz. Three characteristic vibrational waveforms were identified which may indicate bifurcations between vibrational modes of the mucosal wave. No relationship was found between the velocity amplitude and phonation frequency or sound pressure level. A correlation was found between the peak-to-peak displacement amplitude and phonation frequency. A sparse map of the velocity amplitudes on the vocal fold surface was obtained.

Neurophonetics

Neurophonetics aims at the elucidation of the brain mechanisms underlying speech communication in our species. Clinical observations in patients with speech impairments following cerebral disorders provided the initial vantage point of this research area and indicated distinct functional-neuroanatomic systems to support human speaking and listening. Subsequent approaches-considering speech production a motor skill-investigated vocal tract movements associated with spoken language by means of kinematic and electromyographic techniques-allowing, among other things, for the evaluation of computational models suggesting elementary phonological gestures or a mental syllabary as basic units of speech motor control. As concerns speech perception, the working characteristics of auditory processing were first investigated based upon psychoacoustic techniques such as dichotic listening and categorical perception designs. More recently, functional hemodynamic neuroimaging and electrophysiological methods opened the door to the delineation of multiple stages of central auditory processing related to signal detection, classification, sensory memory processes, and, finally, lexical access. Beyond the control mechanisms in a stricter sense, both speech articulation and auditory processing represent examples of 'grounded cognition'. For example, both domains cannot be restricted to text-to-speech translation processes, but are intimately interwoven with neuropsychological aspects of speech prosody, including the vocal expression of affects and the actual performance of speech acts, transforming propositional messages to 'real' utterances. Furthermore, during language acquisition, the periphery of language-i.e., hearing and speaking behavior-plays a dominant role for the construction of a language-specific mental lexicon as well as language-specific action plans for the production of a speech message. WIREs Cogn Sci 2013, 4:191-200. doi: 10.1002/wcs.1211 For further resources related to this article, please visit the WIREs website.

Evaluation of auditory and visual feedback for airflow interruption

INTRODUCTION

Clinical application of mechanical interruption methods for measuring aerodynamic parameters has been hindered by relatively high intrasubject variability. To improve the intrasubject reliability, we evaluated the effect of auditory and visual feedback on subject performance when measuring aerodynamic parameters with the airflow interrupter.

METHODS

Eleven subjects performed four sets of 10 trials with the airflow interrupter: no feedback (control); auditory feedback (tone matching subject's F0 played over headphones); visual feedback (real-time feedback of sound pressure level, frequency, and airflow); and combined auditory and visual feedback. Task order was varied across subjects. The effect of each feedback method on mean and coefficient of variation (CV) of subglottal pressure (Ps), mean flow rate (MFR), and laryngeal airway resistance (RL; Ps/MFR) compared with that of the control trials was determined using paired t tests. Feedback methods were compared against each other using one-way repeated measures analysis of variance.

RESULTS

Each feedback method significantly decreased CV of RL compared with that of the control trials (auditory feedback: P=0.005; visual feedback: P=0.008; and combined feedback: P<0.001). Auditory feedback (P=0.011) and combined feedback (P=0.026) also decreased CV of MFR. Mean MFR was significantly higher during trials with visual feedback compared with that of the auditory feedback.

CONCLUSIONS

Each feedback method improved the intrasubject consistency when measuring RL. Feedback appeared to have a greater effect on MFR than Ps. Although there is no clear optimal feedback method, each is preferable to not providing any feedback during trials. Evaluating new methods of visual feedback to further improve MFR and thus RL measurement would be valuable.

Classification of glottic insufficiency and tension asymmetry using a multilayer perceptron

OBJECTIVE

Laryngeal function can be evaluated from multiple perspectives, including aerodynamic input, acoustic output, and mucosal wave vibratory characteristics. To determine the classifying power of each of these, we used a multilayer perceptron artificial neural network (ANN) to classify data as normal, glottic insufficiency, or tension asymmetry.

STUDY DESIGN

Case series analyzing data obtained from excised larynges simulating different conditions.

METHODS

Aerodynamic, acoustic, and videokymographic data were collected from excised canine larynges simulating normal, glottic insufficiency, and tension asymmetry. Classification of samples was performed using a multilayer perceptron ANN.

RESULTS

A classification accuracy of 84% was achieved when including all parameters. Classification accuracy dropped below 75% when using only aerodynamic or acoustic parameters and below 65% when using only videokymographic parameters.

CONCLUSIONS

Samples were classified with the greatest accuracy when using a wide range of parameters. Decreased classification accuracies for individual groups of parameters demonstrate the importance of a comprehensive voice assessment when evaluating dysphonia.

Analysis of longitudinal phase differences in vocal-fold vibration using synchronous high-speed videoendoscopy and electroglottography

OBJECTIVE

This investigation used synchronous high-speed videoendoscopy and electroglottography (EGG) to systematically study contact and separation behavior along the length of the vocal folds.

DESIGN

Repeated measures.

METHODS

Facilitated by EGG and digital kymograms derived at 20%, 35%, 50%, 65%, and 80% of the posteroanterior length of the vocal folds, the pattern of vocal-fold contact and separation was determined for seven female and seven male vocally healthy subjects while producing "breathy," "comfortable," and "pressed" phonations.

RESULTS

The female subjects consistently used an anterior-to-posterior contact pattern and posterior-to-anterior separation pattern when producing a breathy or comfortable voice, with several using a simultaneous pattern of contact and/or separation for pressed phonation. The male subjects showed more variable "zipperlike" separation patterns, but consistently used a simultaneous contact pattern for pressed voice that was also commonly used when producing comfortable phonation.

CONCLUSIONS

Findings indicate longitudinal phase differences in vocal-fold vibration are both common and expected in vocally healthy speakers. The implications for vocal assessment, as well as for the use and interpretation of the EGG signal, are discussed.

High-speed digital imaging of the larynx: recent advances

PURPOSE OF REVIEW

This review presents recent advances in high-speed digital imaging (HSDI) of the larynx including data acquisition, data analysis, and clinical applicability.

RECENT FINDINGS

Software designed to summarize the large amounts of data captured with HSDI makes it possible to quantitatively analyze recordings from patients, improving the accuracy of the methodology. The new software has been used in studies of normal individuals, increasing our knowledge of normal vocal fold vibratory behavior. HSDI has also been used in patient populations and shows promise in distinguishing various laryngeal conditions that are difficult to distinguish with other imaging modalities. Studies of postoperative patients with HSDI demonstrate the return of some vibratory characteristics but not others, potentially leading the way to improvements in surgical technique.

SUMMARY

Recent advances in HSDI technology have increased the clinical usefulness of the imaging technology and recent studies demonstrate the clinical applicability of HSDI. However, challenges to widespread clinical use of HSDI remain.

Kymographic characterization of vibration in human vocal folds with nodules and polyps

OBJECTIVES/HYPOTHESIS

Digital kymography (DKG) can provide objective quantitative data about vocal fold vibration, which may help distinguish normal from pathological vocal folds as well as nodules from polyps.

STUDY DESIGN

Case-control study.

METHODS

There were 87 subjects who were separated into three groups: control, nodules, and unilateral polyps, and examined using a high-speed camera attached to an endoscope. Videos were analyzed using a custom MATLAB program, and three DKG line-scan positions (25%, 50%, and 75% of vocal fold length) were used in statistical analyses to compare vocal fold vibrational frequency, amplitude symmetry index (ASI), amplitude order, and vertical and lateral phase difference (VPD and LPD, respectively).

RESULTS

Significant differences among groups were found in all vibrational parameters except frequency. Polyps and nodules groups exhibited greater ASI values (less amplitude symmetry) than the control group. Although the control group consistently showed its largest amplitudes at the midline, the polyps group showed larger amplitudes toward the posterior end of the vocal folds. A significant anterior-posterior pattern in amplitude was not found in the nodules group. LPD values were usually largest (most symmetrical) in the control group, followed by nodules and polyps. LPD at the 25% position allowed for differentiation between polyp and nodule groups. The largest VPD (more pronounced mucosal wave) values were usually found in the control group.

CONCLUSIONS

Vibratory characteristics of normal and pathological vocal folds were quantitatively examined and compared using multiline DKG. These findings may allow for better characterization of pathologies and eventually assist in improving the clinical utility of DKG.

Quantitative study of vibrational symmetry of injured vocal folds via digital kymography in excised canine larynges

PURPOSE

Digital kymography and vocal fold curve fitting are blended with detailed symmetry analysis of kymograms to provide a comprehensive characterization of the vibratory properties of injured vocal folds.

METHOD

Vocal fold vibration of 12 excised canine larynges was recorded under uninjured, unilaterally injured, and bilaterally injured conditions. Kymograms were created at 25%, 50%, and 75% of the vocal fold length, and vibratory parameters were compared quantitatively among conditions and were studied with respect to right-left and anterior-posterior symmetries.

RESULTS

Anterior-posterior amplitude asymmetry was found in the bilateral condition. The unilateral condition showed significant right-left amplitude asymmetry, and it showed the lowest right-left phase symmetry among the conditions. In condition comparisons, vertical phase difference did not show significant differences among conditions, whereas amplitudes were significantly different among conditions at all line scan positions and most vocal fold lips. Significant differences in frequency were found among the conditions at all 4 vocal fold lips, with the bilateral condition exhibiting the greatest frequency.

CONCLUSION

Digital kymography and curve fitting provide detailed information about the vibratory behavior of injured vocal folds. Awareness of vibratory properties associated with vocal fold injury may aid in diagnosis, and the quantitative abilities of digital kymography may allow for objective treatment selection.

Direct-numerical simulation of the glottal jet and vocal-fold dynamics in a three-dimensional laryngeal model

An immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed in order to conduct direct-numerical simulations of phonatory dynamics in a three-dimensional model of the human larynx. The computed features of the glottal flow including mean and peak flow rates, and the open and skewness quotients are found to be within the normal physiological range. The flow-induced vibration pattern shows the classical "convergent-divergent" glottal shape, and the vibration amplitude is also found to be typical for human phonation. The vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1:1 modal entrainment between the "adduction-abduction" mode and the "mucosal wave" mode. The glottal jet is found to exhibit noticeable cycle-to-cycle asymmetric deflections and the mechanism underlying this phenomenon is examined.