Master of Science

thesisVocal hyperfunction, characterized by excessive laryngeal muscle tension, is a condition associated with numerous voice disorders, including primary muscle tension dysphonia (pMTD). Primary MTD is disturbance occurring in the absence of structural or neurologic pathology. Vocal hyperfunction is postulated to be the proximal cause of the dysphonia in pMTD. A measure of relative fundamental frequency (RFF) has been proposed as an objective and noninvasive marker of vocal hyperfunction. This retrospective study examined the clinical utility of RFF in identifying and tracking changes in vocal hyperfunction before and following a course of manual circumlaryngeal therapy for pMTD patients. Because RFF is a time-based acoustic measure reliant on periodicity for accurate calculation, additional investigation into the influence of dysphonia severity on its validity across the severity spectrum was completed. RFF calculations were derived from pre- and posttreatment audio recordings from 111 females with pMTD and 20 vocally normal controls. Three voiced-voiceless stimuli (VCV tokens) were analyzed. Listener ratings of dysphonia severity were employed to determine (1) the relation of RFF measures to overall severity, and (2) the effects of dysphonia severity on the utility of RFF calculations. Multiple regression analyses demonstrated that RFF onset slope consistently varied as a function of group membership and therapy time conditions. Pearson Product-Moment Correlations showed a significant relationship between RFF onset cycle 1 values and listener ratings of dysphonia severity. In addition, regression analysis confirmed the influence of therapy condition and specific RFF cycles on dysphonia severity rating. Cumulatively, the analyses confirmed that RFF onset may be sensitive to predicting the presence and degree of vocal hyperfunction before and after therapy, and as an index of dysphonia severity. However, RFF could not be fully analyzed in many subjects, yielding a large quantity of missing data. Adjusted odds ratio estimates revealed that these unanalyzable data were related to phonetic context (token), group membership (pMTD vs. control) and severity level of dysphonia. Although RFF showed potential as an objective measure of vocal hyperfunction before and following voice therapy, the large number of unanalyzable samples (related to increased dysphonia severity especially in the pMTD group) represents a critical limitation

Theoretical and Numerical Analyses of Laryngeal Biomechanics: Towards Understanding Vocal Hyperfunction

Speech is a cornerstone in human communication and an irreplaceable tool for several academic, legal, and artistic careers. Producing intelligible speech is an extremely complex process, involving coupling between the air flow driven by the pressure built up in the lungs, the vibrating viscoelastic tissues in the larynx, namely the vocal folds, and the subglottal and supraglottal (vocal) tracts, including the nasal and oral passages. Therefore, the occurrence of a pathology in one of the organs responsible for voice production may result in deteriorated speech production and, consequently, a negative impact on the daily life and/or professional career of the individual. A specific class of voice disorders that is common among adults is vocal hyperfunction, which is associated with the misuse of vocal organs, resulting in inefficient voice production and, in some cases, vocal trauma. Researchers over the years have conducted clinical and numerical analyses of vocal hyperfunction and have developed assessment tools and therapeutic procedures for vocal hyperfunction; however, a comprehensive understanding of the underlying mechanisms of vocal hyperfunction remains unachieved. Fortunately, easily collected clinical measurements shed some light on potential mechanisms underlying vocal hyperfunction, and numerical and theoretical modelling campaigns of laryngeal biomechanics have shown some success in partially elucidating the biomechanics of voice production. Therefore, a potential route to pursue for a better understanding of the mechanics of vocal hyperfunction lays behind numerical and theoretical analyses guided by available clinical and experimental data. The aim of this thesis is to explore and elucidate, through four research projects, some of the underlying mechanisms associated with voice production in general and vocal hyperfunction in particular, where we resort to 1) data collected using some promising assessment tools and standard clinical measurements, and 2) models of voice production and larynx biomechanics, where theoretical and numerical analyses are conducted guided by the aforementioned clinical measurements. The first project analyses theoretically and numerically the underlying laryngeal factors altering fundamental frequency, for both healthy speakers and speakers with phonotraumatic vocal hyperfunction, during phonation offset, where clinical data of relative fundamental frequency are resorted to in modeling and analysis. We show that the clinically observed drop in fundamental frequency during phonation offset is potentially due to the decline in vocal fold collision forces, which is induced by increasing the glottal gap. We also show how the fundamental frequency drop rate can be modulated by the activation of certain laryngeal muscles, which we speculate to underlie the differences between healthy and hyperfunctional speakers. Besides, we illustrate how certain manifestations of vocal hyperfunction can also affect the drop rate during phonation offset. The second project extends the first one, where phonation onset is explored with similar numerical and theoretical approaches. We illustrate that, when all laryngeal and aerodynamic parameters are fixed in time, fundamental frequency tends to rise due to the increased vocal fold collision levels, and that matches with the clinical observations of the onset of initial or isolated vowels and, in some cases, vowels preceded by voiced consonants. On the other hand, we show through numerical simulations that the decline in fundamental frequency in the case of onset of vowels preceded by voiceless consonants requires involvement of laryngeal muscles, which we speculate to manifest the differences between healthy speakers and patients with vocal hyperfunction. In the third project, we attempt to elucidate the influence of extrinsic laryngeal muscles on posturing mechanics and phonation, and link findings with clinical observations collected from patients with vocal hyperfunction. We show how the vocal fold tension and phonation fundamental frequency vary with varying the magnitude, direction, and location of the net pulling force exerted by the extrinsic laryngeal muscles. Using the previous analysis in combination with clinical data, we pinpoint potential roles of specific extrinsic muscles in modulating fundamental frequency and we suggest some potential roles for extrinsic laryngeal muscles in hyperfunctional phonation. Finally, in the fourth project, we study the mechanics underlying curved and incomplete glottal closure configurations that are observed in some patients with vocal hyperfunction, where we develop and analyse a composite beam model for the vocal folds and we integrate it with a posturing model to enable exploring the effects of certain laryngeal maneuvers. The model predictive capability is adequate, matching clinical observations and simulations produced by high-fidelity models, yet providing useful insights into the underlying mechanism of curved glottal configurations due to its relative simplicity. Our analyses, based on the proposed model, show that the vocal fold layered structure and its interaction with the mechanical loading, resulting during laryngeal maneuvers, induce bending moments that result in different curved (convex and concave) vocal fold shapes that are associated with incomplete glottal closure patterns. We suggest, based on the conducted analyses, some potential laryngeal mechanisms that may be at play in patients with vocal hyperfunction

Optimization and automation of relative fundamental frequency for objective assessment of vocal hyperfunction

The project objective is to improve clinical assessment and diagnosis of the voice disorder, vocal hyperfunction (VH). VH is a condition characterized by excessive laryngeal and paralaryngeal tension, and is assumed to be the underlying cause of the majority of voice disorders. Current clinical assessment of VH is subjective and demonstrates poor inter-rater reliability. Recent work indicates that a new acoustic measure, relative fundamental frequency (RFF) is sensitive to the maladaptive functional behaviors associated with VH and can potentially be used to objectively characterize VH. Here, we explored and enhanced the potential for RFF as a measure of VH in three ways. First, the current protocol for RFF estimation was optimized to simplify the recording procedure and reduce estimation time. Second, RFF was compared with the current state-of-the-art measures of VH – listener perception of vocal effort and the aerodynamic ratio of sound pressure level to subglottal pressure level. Third, an automated algorithm that utilized the optimized recording protocol was developed and validated against manual estimation methods and listener perception. This work enables large-scale studies on RFF to determine the specific physiological elements that contribute to the measure’s ability to capture VH and may potentially provide a non-invasive and readily implemented solution for this long-standing clinical issue

The effects of linguistic factors on analysis of relative fundamental frequency in typical speakers

Thesis (M.S.)--Boston UniversityResearch has shown that the relative fundamental frequency (RFF) surrounding voiceless obstruents may be used as an acoustic correlate for laryngeal tension. This suggests that RFF could potentially be used as a measurement of vocal hyperfunction, a voice pathology characterized by overexertion and increased tension ofthe laryngeal muscles. Despite this potential relationship between laryngeal tension and RFF, there has been little research into what factors contribute to creating stimuli that effectively produce reliable and valid RFF data for subsequent analyses. This study sought to investigate the impacts that linguistic factors have on RFF elicitation in healthy speakers. Two hypotheses were tested: Whether there is a significant difference across voiceless obstruents (i.e. /f/, /s/, /∫/, /k/, /t/, /p/) in terms of eliciting consistent RFF values, and whether sentences containing just one voiceless obstruent or many voiceless obstruents (i.e. "unmixed" vs. "mixed" sentences) are more effective in eliciting stable RFF. Twenty-eight sentences were developed, each containing 3-6 instances of RFF; there were 18 "unmixed" sentences, sub-grouped by obstruent, and 10 "mixed" sentences containing a variety of voiceless obstruents in each sentence. Twelve healthy adults were recorded producing this corpus of sentences and these samples were analyzed using acoustic analysis software. Results of this analysis showed that there were statistically significant differences across the voiceless obstruents in terms of producing consistent, stable instances of RFF, and that the differences appeared to be connected to the manner of articulation of the obstruent (i.e. fricatives were more stable than stops). No significant difference was noted between the types of sentences (i.e. mixed vs. unmixed) but qualitative differences were noted between the two groups (e.g., increased data loss in the mixed sentence group due to increased frequency of vocal irregularities). These results provide some insight into the factors that contribute to creating effective stimuli for eliciting reliable and valid RFF, and the information gathered should be taken into consideration for future studies

LaDIVA: A neurocomputational model providing laryngeal motor control for speech acquisition and production

Many voice disorders are the result of intricate neural and/or biomechanical impairments that are poorly understood. The limited knowledge of their etiological and pathophysiological mechanisms hampers effective clinical management. Behavioral studies have been used concurrently with computational models to better understand typical and pathological laryngeal motor control. Thus far, however, a unified computational framework that quantitatively integrates physiologically relevant models of phonation with the neural control of speech has not been developed. Here, we introduce LaDIVA, a novel neurocomputational model with physiologically based laryngeal motor control. We combined the DIVA model (an established neural network model of speech motor control) with the extended body-cover model (a physics-based vocal fold model). The resulting integrated model, LaDIVA, was validated by comparing its model simulations with behavioral responses to perturbations of auditory vocal fundamental frequency (fo) feedback in adults with typical speech. LaDIVA demonstrated capability to simulate different modes of laryngeal motor control, ranging from short-term (i.e., reflexive) and long-term (i.e., adaptive) auditory feedback paradigms, to generating prosodic contours in speech. Simulations showed that LaDIVA’s laryngeal motor control displays properties of motor equivalence, i.e., LaDIVA could robustly generate compensatory responses to reflexive vocal fo perturbations with varying initial laryngeal muscle activation levels leading to the same output. The model can also generate prosodic contours for studying laryngeal motor control in running speech. LaDIVA can expand the understanding of the physiology of human phonation to enable, for the first time, the investigation of causal effects of neural motor control in the fine structure of the vocal signal.Fil: Weerathunge, Hasini R.. Boston University; Estados UnidosFil: Alzamendi, Gabriel Alejandro. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Cler, Gabriel J.. University of Washington; Estados UnidosFil: Guenther, Frank H.. Boston University; Estados UnidosFil: Stepp, Cara E.. Boston University; Estados UnidosFil: Zañartu, Matías. Universidad Técnica Federico Santa María; Chil

Characterization and Improvement of the Clinical Assessment of Vocal Hyperfunction

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 165-180).Vocal hyperfunction refers to "conditions of abuse and/or misuse of the vocal mechanism due to excessive and/or 'imbalanced' muscular forces" (Hillman, Holmberg, Perkell, Walsh, & Vaughan, 1989), characterized by excessive laryngeal and paralaryngeal tension (Aronson, 1980; M. D. Morrison, Rammage, Belisle, Pullan, & Nichol, 1983; N. Roy, Ford, & Bless, 1996). There is no widely accepted diagnostic measure of the presence and degree of vocal hyperfunction, and currently, assessment during diagnosis is often primarily based on subjective impressions given the patient's history and presentation of symptoms such as auditory-perceptual and visual or tactile discrimination of muscle tension (e.g., laryngeal palpation). Clinical care is hindered by the lack of a "gold standard" objective measure for the assessment of vocal hyperfunction. The first study in this thesis evaluated a novel experimental design for the study of vocal hyperfunction, making use of the established clinical procedure of injection laryngoplasty. This work found that the use of injection laryngoplasty as a platform for the study of some types of vocal hyperfunction is limited, but may offer a convenient opportunity to study selected associated parameters. Particular promising objective measures were investigated in the remaining four studies: kinematics of the vocal folds, root-mean-squared (RMS) measures of surface electromyography (sEMG), and spectral characteristics of sEMG. Kinematic features of vocal fold abduction and adduction were shown to discriminate between individuals with muscle tension dysphonia and controls.(cont.) RMS measures of sEMG were investigated through correlation with current clinical neck palpation techniques in voice therapy patients and via a cross-sectional study of individuals with vocal fold nodules. Correlations between RMS neck sEMG and palpation ratings were low, and although some individuals with nodules displayed RMS neck sEMG patterns that were inconsistent with those seen in controls, overall the RMS measures were unable to discriminate between disordered and control groups. Mean coherence between two neck sEMG locations in individuals with vocal nodules was significantly lower in the 15 - 35 Hz band relative to controls, possibly agreeing with past subjective accounts of "imbalanced" muscle activity.by Cara Elizabeth Stepp.Ph.D

CoQ10 and vitamin A supplementation support voice rehabilitation. A double-blind, randomized, controlled, three-period cross-over pilot study

Objectives: To evaluate the effectiveness of an adjuvant therapy (CoQ10 in its watersoluble form and vitamin A) in supporting voice rehabilitation in a large group of patients with muscle tension dysphonia (MTD). Study Design: Twelve-week, double-blind, randomized, controlled, three-period crossover pilot study. The primary endpoint was the change in the Dysphonia Severity Index (DSI) over the 12-week study period. Secondary endpoints were the changes in the subcomponents of DSI, including MPT, F0-high, I-low, and jitter. Exploratory endpoints were the changes in the Shimmer and in Voice Handicap Index (VHI). Methods: Patients were randomly assigned in a 1:1 ratio to two counter-balanced arms. Group A (ADJ-PLA) patients were administered QTer 300 mg and Vit A acetate 500.000 Ul/g 1 mg twice daily for a 4-week intervention period, followed by a 4-week period of wash-out, and then were submitted to a last 4-week period of placebo. Patients in Group B (PLB-ADJ) were given the treatment period in reverse order. Both groups received a 45-min voice therapy in a group format once a day for 4 weeks during the first and the second active periods. The therapy was held during the wash-out period. Results: The analysis of main time effect indicated a trend toward recovery of vocal function regardless of group assignment. A significant time by group effect was found on DSI [F = 3.4 (2.5, 80.5), p = 0.03], F0-high [F = 4.5 (2.6, 82.9), p = 0.008] and Shimmer [F = 3.6 (1.5, 46.9), p = 0.048], under CoQ10 and Vit A treatment, with a small effect size. There was no significant time by group effect on the other study measures, namely MPT, I-low, VHI. Conclusions: A trend toward recovery of vocal function was observed in all the patients, likely due to voice rehabilitation. The improvement of DSI was greater under CoQ10 and Vitamin treatment, indicating a more pronounced improvement of vocal quality under adjuvant therapy. The study protocol was reviewed and approved by the Ethics Committee of Policlinico Umberto I Hospital, Rome, Italy Rif. 3069/13.02.2014