Vocal Fold Tension Research Articles

Searching for the Causes of Chest-Falsetto Register Breaks under Anechoic Conditions

The origin of the breaks between chest and falsetto registers has remained one of the most controversial themes in voice science. The search for the causes of register breaks is reminiscent of a detective story. Classically, the breaks have been thought to be a consequence of a sudden change in laryngeal muscle activity causing a sudden change of vocal fold tension and frequency of oscillation. Experiments with excised human larynges showed, however, that sudden chest-falsetto breaks can spontaneously occur also when the vocal fold tension is changed smoothly (1). An alternative theoretical explanation of such phenomena emerged in the 1990s with the introduction of the theory of nonlinear dynamics to voice science. This theory showed that the phonatory system behaves like a nonlinear dynamic oscillator, where the chest and falsetto registers can be viewed as two possible ways of oscillation (attractors) that are inherent to the vocal apparatus (1). Voice breaks can then be recognized as “bifurcation events“ in which the oscillator suddenly changes the vibratory regime by shifting from one attractor to another. Whether the oscillation is in falsetto or chest register does not necessarily depend only on the laryngeal adjustment but also on other factors. Tiny changes in these factors (including, e.g., subglottal pressure, airflow, but also acoustic resonances in the breathing airways), can cause the oscillation to suddenly change from one register to another.

Modeling the influence of the extrinsic musculature on phonation.

Neck muscles play important roles in various physiological tasks, including swallowing, head stabilization, and phonation. The mechanisms by which neck muscles influence phonation are not well understood, with conflicting reports on the change in fundamental frequency for ostensibly the same neck muscle activation scenarios. In this work, we introduce a reduced-order muscle-controlled vocal fold model, comprising both intrinsic muscle control and extrinsic muscle effects. The model predicts that when the neck muscles pull the thyroid cartilage in the superior-anterior direction (with a sufficiently large anterior component), inferior direction, or inferior-anterior direction, tension in the vocal folds increases, leading to fundamental frequency rise during sustained phonation. On the other hand, pulling in the superior direction, superior-posterior direction, or inferior-posterior direction (with a sufficiently large posterior component) tends to decrease vocal fold tension and phonation fundamental frequency. Varying the pulling force location alters the posture and phonation biomechanics, depending on the force direction. These findings suggest potential roles of particular neck muscles in modulating phonation fundamental frequency, with implications for vocal hyperfunction.

A Pilot Study on the Functional Stability of Phonation in EEG Bands After Repetitive Transcranial Magnetic Stimulation in Parkinson's Disease.

Parkinson's disease (PD) is a neurodegenerative condition with constantly increasing prevalence rates, affecting strongly life quality in terms of neuromotor and cognitive performance. PD symptoms include voice and speech alterations, known as hypokinetic dysarthria (HD). Unstable phonation is one of the manifestations of HD. Repetitive transcranial magnetic stimulation (rTMS) is a rehabilitative treatment thathas been shown to improve some motor and non-motor symptoms of persons with PD (PwP). This study analyzed the phonation functional behavior of 18 participants (13 males, 5 females) with PD diagnosis before (one pre-stimulus) and after (four post-stimulus) evaluation sessions of rTMS treatment, to assess the extent of changes in their phonation stability. Participants were randomized 1:1 to receive either rTMS or sham stimulation. Voice recordings of a sustained vowel [a:] taken immediately before and after the treatment, and at follow-up evaluation sessions (immediately after, at six, ten, and fourteen weeks after the baseline assessment) were processed by inverse filtering to estimate a biomechanical correlate of vocal fold tension. This estimate was further band-pass filtered into EEG-related frequency bands. Log-likelihood ratios (LLRs) between pre- and post-stimulus amplitude distributions of each frequency band showed significant differences in five cases actively stimulated. Seven cases submitted to the sham protocol did not show relevant improvements in phonation instability. Conversely, four active cases did not show phonation improvements, whereas two sham cases did. The study provides early preliminary insights into the capability of phonation quality assessment by monitoring neuromechanical activity from acoustic signals in frequency bands aligned with EEG ones.

Classification of Phonation Modes in Classical Singing Using Modulation Power Spectral Features

In singing, the perceptual term “voice quality” is used to describe expressed emotions and singing styles. In voice physiology research, specific voice qualities are discussed by the term phonation modes and are related directly to the voicing produced by the vocal folds. The control and awareness of phonation modes is vital for professional singers to maintain a healthy voice. Most studies on phonation modes have investigated speech and have used glottal inverse filtering to compute features from an estimated excitation signal. The performance of this method is reported to decrease at high pitches, which limits its usability for the singing voice. To overcome this, this study proposes to use features derived from the modulation power spectrum for phonation mode classification in the singing voice. The exploration of the modulation power spectrum is motivated by the fact that, in singing, temporal modulations (known as vocal vibrato) and spectral modulations hold information of the vocal fold tension. Since there exists no large publicly available dataset of phonation modes in singing, we created a new dataset consisting of six female and four male classical singers, who sang five vowels at different pitches in three phonation modes (breathy, modal, and pressed). Experimental results with a support vector machine classifier reveal that the proposed features show better classification performance compared to state-of-the-art reference features. The performance for the current dataset is at least 10% higher compared to the performance of the reference features (such as glottal source features and MFCCs) in the case of target labels and around 6% higher in the case of perceptually assessed labels.

Exploring the mechanics of fundamental frequency variation during phonation onset.

Fundamental frequency patterns during phonation onset have received renewed interest due to their promising application in objective classification of normal and pathological voices. However, the associated underlying mechanisms producing the wide array of patterns observed in different phonetic contexts are not yet fully understood. Herein, we employ theoretical and numerical analyses in an effort to elucidate the potential mechanisms driving opposing frequency patterns for initial/isolated vowels versus vowels preceded by voiceless consonants. Utilizing deterministic lumped-mass oscillator models of the vocal folds, we systematically explore the roles of collision and muscle activation in the dynamics of phonation onset. We find that an increasing trend in fundamental frequency, as observed for initial/isolated vowels, arises naturally through a progressive increase in system stiffness as collision intensifies as onset progresses, without the need for time-varying vocal fold tension or changes in aerodynamic loading. In contrast, reduction in cricothyroid muscle activation during onset is required to generate the decrease in fundamental frequency observed for vowels preceded by voiceless consonants. For such phonetic contexts, our analysis shows that the magnitude of reduction in the cricothyroid muscle activation and the activation level of the thyroarytenoid muscle are potential factors underlying observed differences in (relative) fundamental frequency between speakers with healthy and hyperfunctional voices. This work highlights the roles of sometimes competing laryngeal factors in producing the complex array of observed fundamental frequency patterns during phonation onset.

Effects of Laryngeal Vibratory Asymmetry and Neuromuscular Compensation on Voice Quality.

Vibratory asymmetry and neuromuscular compensation are often seen in laryngeal neuromuscular pathology. However, the ramifications of these findings on voice quality are unclear. This study investigated the effects of varying levels of vibratory asymmetry and neuromuscular compensation on cepstral peak prominence (CPP), an analog of voice quality. In vivo canine phonation model. Varying degrees of vocal fold vibratory asymmetry were achieved by stimulating one recurrent laryngeal nerve (RLN) over 11 levels from threshold to maximal muscle activation. For each of these levels, phonation was induced at systematically varied combinations of neuromuscular compensation: three levels each of contralateral RLN stimulation (80%, 90%, and 100% of maximal), superior laryngeal nerve (SLN) activation (0%, 50%, and 100% of maximal), and airflow levels (500, 700, and 900 mL/s). Vocal fold symmetry was determined by assessing the opening phase of the vibratory cycle in high-speed video recordings. Voice quality was estimated acoustically by calculating CPP for each voice sample. Eight hundred twenty-two phonatory conditions with varying degrees of vibratory asymmetry were evaluated. CPP was highest at vibratory symmetry. Increasing levels of asymmetry resulted in significant decreases in CPP. CPP increased significantly with increasing contralateral RLN activation. CPP was significantly higher at 50% SLN activation than 0% or 100% SLN activation. Voice quality, as approximated by CPP, is best at vibratory symmetry and deteriorates with increasing degrees of asymmetry. Voice quality may be improved with neuromuscular compensation by increased adduction of the contralateral vocal fold or increased vocal fold tension at mid-levels of SLN activation. NA, Basic Science Laryngoscope, 132:130-134, 2022.

Voice Assessment in Patients With Obstructive Sleep Apnea Syndrome After Transoral Robotic Surgery.

Objectives: Removal of part of the tongue base, in combination with uvulopharyngopalatoplasty via transoral robotic surgery (TORS), for treating obstructive sleep apnea syndrome (OSAS) results in enlargement of the oropharynx and hypopharynx and change in the size of the resonance chamber. These procedures may also alter the laryngeal-hyoid bone complex, which is linked to vocal fold tension. Thus, there is the potential for change in phonation and pitch after surgery.Study Design: Prospective, nonrandomized, institutional board-approved study.Methods: From January to August 2018, 15 patients with OSAS receiving TORS underwent voice and pitch sampling. The multi-dimensional voice program (MDVP) was applied to the evaluation of preoperative sound parameters. Highest pitch and lowest pitch were obtained with real-time pitch software, with pitch synchronized to electronic organ or tuner. Subjects also completed the Voice Handicap Index-10 scale (VHI-10), to assess their subjective perception and to detect factors affecting the VHI-10 score. The relevant parameters were analyzed again 3 months after the operation.Results: There was an increase in VHI-10 score 3 months after operation that did not reach statistical significance. There were also no significant differences in sound parameters. Increases in highest pitch (353.18 Hz shift to 387.99 Hz), highest semitone ( shift to ), lowest pitch (117.45 Hz shift to 131.42 Hz), and lowest semitone (C3 shift to C3) did not reach statistical significance. The increase in the lowest semitone was significantly related to change in VHI-10 score (r = −0.808, P = 0.028).Conclusion: Patients with OSA undergoing TORS showed a negative correlation coefficient over 0.8 with change in VHI-10 score. That is, increase in the lowest semitone after operation correlated with increase in VHI-10 score which may cause perceive changes in subjective pronunciation.

Specificities of phonation biomechanics in Down Syndrome children

Down Syndrome (DS) has been the aim of numerous studies, although its phonation specificities have not received much attention. DS is a genetic disorder caused by the presence of a third copy of chromosome 21, being the explanation of different behavioral and clinical anomalies: developmental disorders, hearing, speech and language impairments and neuromotor and morphological alterations of the oro-naso-pharyngeal (ONP) and laryngeal (ONL) structures. The goal of the current study is to carry on a first approach to the biomechanics of phonation in DS children from an acoustic perspective, trying to describe its specificities and to establish a link with the syndrome. A specific application designed to analyze the glottal source and its relationship to vocal fold biomechanics has been used. Nineteen biomechanical features from vocal fold dynamics have been used, related to fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, mass and stiffness profiles, unbalance, contact gaps, and tremor. On one hand, the non-normophonic corpus is composed of eight children with DS with age range between five and six years old. On the other hand, a normative or normophonic population was taken. The last group consisted of eight children with similar ages to the previous ones. The results achieved show relevant differences (p < .05) in larynx biomechanics regarding the following features: deviations in the fundamental frequency, vocal fold tension (regarding musculus vocalis), and phonation tremor. These distortions could be directly related with the neuromotor alterations known to be associated to DS and could reflect underlying factors of DS phonation features.

Acoustic correlates of laryngeal control: Parkinson's and healthy older adults

Vocal fold tension is commonly used to control pulmonary airflow and subglottal pressure, resulting in a positive f0-intensity correlation. Since Parkinson's disease (PD) constrains fine movements, this mechanism may be impaired in PD. We analyzed the f0-intensity correlation in PD and a healthy age- and gender-matched control group. For that, we extracted gender-normalized f0, intensity, and spectral emphasis (SE) from each syllable in three sentences of a read text. Additionally, from a sustained [a] task, we measured maximum phonation time ([a] duration; MPT) as well as jitter and shimmer (combined using PCA; JS). Using Linear Mixed Models, we confirmed the f0-intensity correlation in each group. Furthermore, JS interacted with intensity, indicating that voice instability weakens the correlation. No MPT effect was found. Importantly, even controlling for JS and MPT, the f0-intensity correlation was significantly weaker in PD. Lastly, we build a model using SE instead of intensity and only a negative correlation was found. Overall, this study suggests that voice instability negatively affects airflow control, but is not sufficient to explain its reduction in PD. Moreover, it indicates that the SE-f0 relationship is preserved in PD and it is not affected by the voice parameters analyzed.

Effects of Voice Therapy for Dysphonia due to Tension Imbalance in Unilateral Vocal Fold Paralysis and Paresis

Medialization procedures, such as type I thyroplasty, arytenoid adduction, and vocal fold injection, are popular treatments for dysphonia due to unilateral vocal fold paralysis (UVFP). However, dysphonia occasionally persists after medialization procedures owing to tension imbalance. This tension imbalance causes diplophonia, asymmetry and aperiodic vibrational flutter in travelling wave motion. Currently, there is no established treatment for tension imbalance. We herein report two cases with residual dysphonia due to tension imbalance following medialization for chronic UVFP, and another case presenting with dysphonia due to tension imbalance following chronic unilateral vocal fold paresis. Three patients underwent voice therapy using flow phonation to facilitate increased airflow management in speech as well as forward oral resonance by focusing on balanced airflow. Phonatory outcomes were evaluated using stroboscopic findings, aerodynamic and acoustic measures, as well as self-rating. Aerodynamic assessments, acoustic findings and self-ratings improved in all three cases after voice therapy. Stroboscopic findings prior to voice therapy showed asymmetric vibration with glottic gap, which was improved after voice therapy. Fundamental frequency (F0) also increased post-therapy. In a previous canine study, it was shown that enhanced breath support with expiratory airflow resulted in increased F0, suggesting that enhanced breath support could increase vocal fold tension. The increased F0 achieved in the present cases following voice therapy may increase vocal fold tension with breath support. Thus, voice therapy using flow phonation may be effective for supporting vocal fold tension and improving dysphonia due to tension imbalance following UVFP and paresis.

Estimating vocal fold stiffness: Using the relationship between subglottic pressure and fundamental frequency of phonation as an analog.

The stiffness of the vocal folds is an important factor in voice production, yet clinically applicable measurements are still lacking. It has been demonstrated in an in vivo canine model that fundamental frequency (F0 ) increased linearly as subglottic pressure (Ps ) increased, but with a lesser slope for higher levels of vocal fold tension. In this study, the relationship between F0 and Ps was investigated using the airflow interruption method in awake patients non-invasively. Healthy volunteers enrolled for evaluation. Single-centre. Thirty-three healthy volunteers aged 20 and older were recruited, with one excluded for a recent asthma attack. The relationships between F0 and Ps , described as the slope (Hz/kPa), were investigated when the participants sustained voicing the vowel/o/at 3 incremental frequencies 4 semitones apart in the modal register (F1, F2 and F3). Thirty-two healthy volunteers (20 females, 12 males) aged 20-47years were enrolled for final analyses. There was a statistically significant difference in the slopes of the linear regression lines of F0 -Ps , depending on the frequency with which the vowel/o/ was produced (P<.001). The slope differed significantly between F2 and F1 (P<.001; P=.015), F3 and F1 (P<.001; P=.002) and F3 and F2 (P<.001; P=.005) for both women and men, respectively. It was demonstrated that the higher the vocal fold tension, the smaller the slope between F0 and Ps . Using the relationship between F0 and Ps as an analog of vocal fold stiffness is potentially practical for clinical application.

Singing voice: acoustic parameters after vocal warm-up and cool-down

Purpose: The aim of this study was to evaluate the effect of the vocal warm-up and cool-down on the singing voice through Fundamental Frequency (F0), Jitter, Shimmer and harmonics-to-noise ratio (HNR).Methods: Thirty-two female singing students were recorded four times while uttering the vowel [a] for at least 5''. The first two recordings were collected before and after a vocal warm-up session and the last two before and after a vocal cool-down session. Between those sessions the participants underwent an intense vocal activity.Results: Results showed significant variations in the average values of the parameters measured. The mean value of the F0 after intense vocal activity turned to be higher than the one measured before the warm-up session, as well as the mean F0 measured after singing compared to the one measured after the vocal warm-up. On the other end, the mean F0 after the vocal cool-down resulted to be lower than that measured before. After the vocal warm-up session Jitter and Shimmer decreased while HNR increased. In addition, a decrease was detected in comparison with the average value of Jitter and Shimmer before vocal warm-up and after vocal cool-down, whereas HNR increased. There was also a decrease between the Shimmer before the vocal warm-up and after an intense phonatory activity while HNR increased.Conclusions: Our study highlights the effect of the vocal warm-up on acoustic parameters. The reduction in F0 observed after the cool-down session confirms its positive effect in helping professional vocal recovery and reducing vocal fold tension.

Relative fundamental frequency of voiced and voiceless stops and fricatives for different phonation types in normal French speakers

The relative fundamental frequency (RFF) was recently used to assess vocal effort in normal and dysphonic subjects since it reflects the vocal fold tension at the offset and onset of vowels with, in particular, lower values at the edges of voiced consonants compared to their voiceless counterparts. In this study, we explored the RFF variations according to the voicing status and the articulation manner of consonants, in several types of speech production known to involve different levels of vocal effort. Twelve native French speakers (6 females) with normal voice were asked to produce 24 trains of eight syllables in seven vocal conditions: spontaneous, low, high, soft, loud, breathy, and pressed voice. We considered the unaspirated voiceless and voiced consonants /p, b, f, v/ with the middle open vowel /a/. As expected, the RFF was lower for voiced than for voiceless consonants. In addition, it was lower for stops than for fricatives. The RFF was also lower for the high, loud, and pressed conditions while it was higher for the low, soft, and breathy conditions in comparison to the values for the spontaneous voice. The RFF measurement seems to be efficient to discern subtle levels of vocal effort in normal subjects.

Associations between respiratory arrhythmia and fundamental frequency of spontaneous crying in preterm and term infants at term-equivalent age.

ABSTRACTThis study investigated whether lower vagal function in preterm infants is associated with increased fundamental frequency (F 0; frequency of vocal fold vibration) of their spontaneous cries. We assessed respiratory sinus arrhythmia (RSA) during quiet sleep as a measure of vagal function, and its relationship with the F 0 of spontaneous cries in healthy preterm and term infants at term‐equivalent age. The results showed that preterm infants have significantly lower RSA, and higher overall F 0 than term infants. Moreover, lower RSA was associated with higher overall F 0 in preterm infants, whereas higher RSA was positively associated with mean and maximum F 0, and a larger F 0 range in term infants. These results suggest that individual differences in vagal function may be associated with the F 0 of spontaneous cries via modulation of vocal fold tension in infants at an early developmental stage. © 2016 The Authors. Developmental Psychobiology Published by Wiley Periodicals, Inc. Dev Psychobiol 58:724–733, 2016.

A Mechanism for Sensorimotor Translation in Singing

We propose a new framework to understand singing accuracy, based on multi-modal imagery associations: the MMIA model. This model is based on recent data suggesting a link between auditory imagery and singing accuracy, evidence for a link between imagery and the functioning of internal models for sensorimotor associations, and the use of imagery in singing pedagogy. By this account, imagery involves automatic associations between different modalities, which in the present context comprise associations between pitch height and the regulation of vocal fold tension. Importantly, these associations are based on probabilistic relationships that may vary with respect to their precision and accuracy. We further describe how this framework may be extended to multi-modal associations at the sequential level, and how these associations develop. The model we propose here constitutes one part of a larger architecture responsible for singing, but at the same time is cast at a general level that can extend to multi-modal associations outside the domain of singing.

Pitch Elevation in Trangendered Patients: Anterior Glottic Web Formation Assisted by Temporary Injection Augmentation

Pitch elevation surgery is most often indicated to assist male-to-female transgendered individuals seeking a more feminine voice quality. Behavioral therapy is primary management but if the desired voice quality is not achieved, surgery is offered. Procedures described that raise vocal pitch alter one or more of the main parameters known to physiologically control pitch; vocal fold tension, length, and mass. Web formation with injection augmentation significantly raises vocal pitch in male-to-female transgendered individuals. Retrospective cohort study. This report describes the voice results after anterior web formation with injection augmentation to reduce vocal fold length in a series of 10 transgendered patients. Retrospective review of male-to-female transgendered patients referred to St. Michaels Hospital Voice Clinic, Toronto, Canada for pitch elevation was carried out including demographic data, preoperative and postoperative acoustic data and videostroboscopic evaluation. Comparison between preoperative to postoperative acoustic measures demonstrated a mean increase in fundamental frequency of 110Hz after web formation. Perturbation measures and pitch range were unchanged from before surgery to after surgery. This novel modification for endoscopic anterior web formation has been shown to be a successful procedure for permanent elevation of pitch with little or no morbidity.

109: Cricothyroid Botulinum Toxin Injection to Avert Tracheostomy in Bilateral Vocal Cord Paralysis

Up to 59 percent of children with bilateral vocal cord paralysis require a tracheostomy for airway management. While the recurrent laryngeal nerve is usually compromised, the cricothyroid muscle, a tensor of the vocal cords has a separate innervation. We report an innovative approach whereby a tracheostomy is averted by injecting Onabotulinum Toxin into the cricothyroid muscles in patients with bilateral vocal cord paralysis. The goal is to denervate the cricothyroid muscles thereby decreasing vocal fold tension and a subsequent increase in the glottic space. We review pediatric cases of bilateral vocal paralysis managed with Onabotulinum Toxin A injections by the senior author. Medical charts were retrospectively reviewed; the clinical manifestation, injection dosage and outcomes are reported. Six patients were included. Five were female and one male infants, ranging from three weeks old to four years old. The clinical presentations included stridor and respiratory distress. We used Onabotulinum toxin to paralyze the cricothyroid muscles of five patients who would have undergone a tracheostomy for airway obstruction secondary bilateral vocal cord paralysis. We had a successful decanulation of an additional patient with a long-term tracheostomy for the same pathology. No complications were reported. Onabotulinum toxin injection in the cricothyroid muscles provides a safe, fast, effective and successful option for patients suffering with vocal cord paralysis.

The effect of temperature on basal tension and thyroarytenoid muscle contraction in an isolated rat glottis model.

The pitch of voice is closely related to the vocal fold tension, which is the end result of coordinated movement of the intralaryngeal muscles, and especially the thyroarytenoid muscle. It is known that vocal quality may be affected by surrounding temperature; however, the effect of temperature on vocal fold tension is mostly unknown. Thus, the aim of this study was to evaluate the effect of temperature on isolated rat glottis and thyroarytenoid muscle contraction induced by electrical field stimulation. In vitro isometric tension of the glottis ring from 30 Sprague-Dawley rats was continuously recorded by the tissue bath method. Electrical field stimulation was applied to the glottis ring with two wire electrodes placed parallel to the glottis and connected to a direct-current stimulator. The tension changes of the rat glottis rings that were either untreated or treated with electrical field stimulation were recorded continuously at temperatures from 37 to 7 °C or from 7 to 37 °C. Warming from 7 to 37 °C increased the basal tension of the glottis rings and decreased the electrical field stimulation-induced glottis ring contraction, which was chiefly due to thyroarytenoid muscle contraction. In comparison, cooling from 37 to 7 °C decreased the basal tension and enhanced glottis ring contraction by electrical field stimulation. We concluded that warming increased the basal tension of the glottis in vitro and decreased the amplitude of electrical field stimulation-induced thyroarytenoid muscle contraction. Thus, vocal pitch and the fine tuning of vocal fold tension might be affected by temperature in vivo.

Beeinflussung des Stimmlippeneinschwingvorganges durch Aktivierung kehlkopfferner Muskeln

Various voice therapy techniques include not only phonation exercises but also measure to regulate tonus of non-larynx related muscles. This is based on the belief that the use of non-laryngeal muscles may affect laryngeal muscle action during phonation onset und phonation. Here we raised the question if indeed a well defined activation of muscles distant to the larynx may effect phonation onset time and the vibratory cycles following thereafter. Prospective partly randomized single center pilot study with 8 healthy volunteers. Analysed variables were time of phonation onset and closed quotient (Qx) derived via electroglottgraphy. According to a randomization protocol volunteers had to press a training device ( + condition) or to keep the hand quiet ( - condition). Comparism of both conditions did not reveal any significant difference, however Qx tended to be higher in the + condition. The data presented here does not confirm that activation of hand muscles influences phonation onset time. However the preceding vibratory cycles may be altered towards a higher tone of intralaryngeal muscles regulating vocal fold tension. Further studies including more volunteers or patients with functional voice disorders and protocols employing the activation of other muscle groups are warranted in order to shed more light into the interrelationship between larynx and other muscle activation during phonation.

Combined type IIIB with bilateral type I thyroplasty for pitch lowering with maintenance of vocal fold tension.

To evaluate type IIIB thyroplasty using the excised larynx bench apparatus and determine how altering vocal fold contour by performing bilateral medialization of the inferior vocal fold affects phonation. This procedure could be performed in patients for whom pitch lowering is desirable, such as female-to-male transsexuals or male patients with mutational falsetto in whom intensive voice therapy was insufficient. Aerodynamic, acoustic, and high-speed videokymographic data were collected for nine larynges at three subglottal pressure inputs for each of three conditions: normal; type IIIB thyroplasty; and combined type IIIB with modified bilateral type I thyroplasty intended to create a more rectangular glottal configuration. Each larynx served as its own control. Phonation threshold flow (p=0.005), phonation threshold power (p=0.031), and airflow varied across conditions with highest values for type IIIB thyroplasty and lowest for the combined procedure. Fundamental frequency was significantly different (p<0.001), decreasing by approximately 100Hz from control to type IIIB trials, and then by approximately 15Hz from IIIB to combined procedure trials. Vibratory amplitudes and intrafold phase difference were highest for type IIIB trials. Addition of bilateral inferior medialization to type IIIB thyroplasty provided some further decrease in frequency, but mostly served to increase tension, reduce airflow, and produce a vibratory pattern which more closely mirrored control trials. Exploration of this combined procedure in patients may be warranted if not completely satisfied with the results from type IIIB thyroplasty alone.