Effects on Voice Quality of Thyroidectomy: A Qualitative and Quantitative Study Using Voice Maps.

OBJECTIVES: This study aims to explore the effects of thyroidectomy-a surgical intervention involving the removal of the thyroid gland-on voice quality, as represented by acoustic and electroglottographic measures. Given the thyroid gland's proximity to the inferior and superior laryngeal nerves, thyroidectomy carries a potential risk of affecting vocal function. While earlier studies have documented effects on the voice range, few studies have looked at voice quality after thyroidectomy. Since voice quality effects could manifest in many ways, that a priori are unknown, we wish to apply an exploratory approach that collects many data points from several metrics. METHODS: A voice-mapping analysis paradigm was applied retrospectively on a corpus of spoken and sung sentences produced by patients who had thyroid surgery. Voice quality changes were assessed objectively for 57 patients prior to surgery and 2months after surgery, by making comparative voice maps, pre- and post-intervention, of six acoustic and electroglottographic (EGG) metrics. RESULTS: After thyroidectomy, statistically significant changes consistent with a worsening of voice quality were observed in most metrics. For all individual metrics, however, the effect sizes were too small to be clinically relevant. Statistical clustering of the metrics helped to clarify the nature of these changes. While partial thyroidectomy demonstrated greater uniformity than did total thyroidectomy, the type of perioperative damage had no discernible impact on voice quality. CONCLUSIONS: Changes in voice quality after thyroidectomy were related mostly to increased phonatory instability in both the acoustic and EGG metrics. Clustered voice metrics exhibited a higher correlation to voice complaints than did individual voice metrics.

Flow-induced oscillations of vocal-fold replicas with tuned extensibility and material properties.

Human vocal folds are highly deformable non-linear oscillators. During phonation, they stretch up to 50% under the complex action of laryngeal muscles. Exploring the fluid/structure/acoustic interactions on a human-scale replica to study the role of the laryngeal muscles remains a challenge. For that purpose, we designed a novel in vitro testbed to control vocal-folds pre-phonatory deformation. The testbed was used to study the vibration and the sound production of vocal-fold replicas made of (i) silicone elastomers commonly used in voice research and (ii) a gelatin-based hydrogel we recently optimized to approximate the mechanics of vocal folds during finite strains under tension, compression and shear loadings. The geometrical and mechanical parameters measured during the experiments emphasized the effect of the vocal-fold material and pre-stretch on the vibration patterns and sounds. In particular, increasing the material stiffness increases glottal flow resistance, subglottal pressure required to sustain oscillations and vibratory fundamental frequency. In addition, although the hydrogel vocal folds only oscillate at low frequencies (close to 60 Hz), the subglottal pressure they require for that purpose is realistic (within the range 0.5-2 kPa), as well as their glottal opening and contact during a vibration cycle. The results also evidence the effect of adhesion forces on vibration and sound production.

A micro-mechanical model for the fibrous tissues of vocal folds.

Composed of collagen, elastin and muscular fibrous networks, vocal folds are soft laryngeal multi-layered tissues owning remarkable vibro-mechanical performances. However, the impact of their histological features on their overall mechanical properties still remains elusive. Thereby, this study presents a micro-mechanical hyperelastic model able to describe the 3D fibrous architecture and the surrounding matrices of the vocal-fold sublayers, and to predict their mechanical behavior. For each layer, the model parameters were identified using available histo-mechanical data, including their quasi-static response for key physiological loading paths, i.e., longitudinal tension, transverse compression and longitudinal shear. Regardless of the loading path, it is shown how macroscale nonlinear, anisotropic tissue responses are inherited from the fiber scale. Scenarios of micro-mechanisms are predicted, highlighting the major role of 3D fiber orientation in tension, steric hindrance in compression, and matrix contribution in shear. Finally, combining these predictions to vibrating hyperelastic Timoshenko beam's theory, the impact of the fibrous architecture of the upper layers on vocal-fold vibratory properties is emphasized.

Clinical characteristics of singers attending a phoniatric outpatient clinic.

Purpose: Studies suggest that singers are over-represented in voice clinics and present a high risk of developing voice disorders. This retrospective study aims to describe the characteristics of 78 singers consulting a phoniatrician.Methods: In their medical files, data related to age, gender, occupational status, singing training, musical style, voice complaint, diagnosis, voice-quality grading (GRBAS) and treatment were gathered.Results: The patients were mostly female singers (87%). Non-professional singers (semi-professional included) represented 64%, professional singers 25% and students of singing 11%. The majority of singers were choristers (27%) and 22% were classical-style/oratorio-style singers. Two-thirds of the population had intensive vocal activity in speech or singing. Vocal endurance, somatosensory signs and difficulties with high pitches were the most frequent symptoms. Among the patients, 79% presented with singing-voice disorders with 85% of these having vocal fold lesions. Generally, their speaking voices were preserved. Vocal-folds nodules were the most prevalent pathology (37%) followed by sulcus (26%) and voice therapy was the main treatment.Conclusions: This study emphasizes the fact that singers have specific voice complaints related to their voice usage. The high occurrence of sulcus and other congenital-lesion suspicions, unusual in the general population consulting an ENT phoniatrician, seems to be rather specific for singers in agreement with the literature.

Mechanics of gelatin-based hydrogels during finite strain tension, compression and shear.

Introduction: Among the biopolymers used to make hydrogels, gelatin is very attractive due to its biocompatibility, biodegradability and versatile physico-chemical properties. A proper and complete characterization of the mechanical behavior of these hydrogels is critical to evaluate the relevance of one formulation over another for a targeted application, and to optimise their processing route accordingly. Methods: In this work, we manufactured neat gelatin and gelatin covalently cross-linked with glutaraldehyde at various concentrations, yielding to hydrogels with tunable mechanical properties that we characterized under finite strain, cyclic tension, compression and shear loadings. Results and Discussion: The role of both the chemical formulation and the kinematical path on the mechanical performances of the gels is highlighted. As an opening towards biomedical applications, the properties of the gels are confronted to those of native soft tissues particularly complicated to restore, the human vocal folds. A specific cross-linked hydrogel is selected to mimic vocal-fold fibrous tissues.

Vocal drum sounds in human beatboxing: An acoustic and articulatory exploration using electromagnetic articulography.

Acoustic characteristics, lingual and labial articulatory dynamics, and ventilatory behaviors were studied on a beatboxer producing twelve drum sounds belonging to five main categories of his repertoire (kick, snare, hi-hat, rimshot, cymbal). Various types of experimental data were collected synchronously (respiratory inductance plethysmography, electroglottography, electromagnetic articulography, and acoustic recording). Automatic unsupervised classification was successfully applied on acoustic data with t-SNE spectral clustering technique. A cluster purity value of 94% was achieved, showing that each sound has a specific acoustic signature. Acoustical intensity of sounds produced with the humming technique was found to be significantly lower than their non-humming counterparts. For these sounds, a dissociation between articulation and breathing was observed. Overall, a wide range of articulatory gestures was observed, some of which were non-linguistic. The tongue was systematically involved in the articulation of the explored beatboxing sounds, either as the main articulator or as accompanying the lip dynamics. Two pulmonic and three non-pulmonic airstream mechanisms were identified. Ejectives were found in the production of all the sounds with bilabial occlusion or alveolar occlusion with egressive airstream. A phonetic annotation using the IPA alphabet was performed, highlighting the complexity of such sound production and the limits of speech-based annotation.

Lateralization of the Vocal Fold: Results of an Exclusive Transoral Approach.

OBJECTIVE: Vocal fold paralysis in adduction can result in dyspnea. The authors have previously described an original vocal fold lateralization technique performed exclusively through an endoscopic approach. In this work, we studied long and short-term results of this procedure on dyspnea, phonation, and swallowing. STUDY DESIGN: Retrospective cohort study through data from medical records and operative notes. Patients with unilateral or bilateral vocal fold paralysis in adduction who underwent transoral lateralization were included. METHODS: In all patients, under laryngosuspension, a supraglottic laryngotomy was performed with CO2 laser and a lateralization suture was passed through the thyroid cartilage to the vocal process of the vocal fold with the desired tension allowing lateralization of the arytenoid and corresponding vocal fold. We studied evolution of breathing, phonation, and swallowing in all patients who underwent lateralization suture. We tried to correlate symptoms to preoperative and postoperative glottic area, inter-arytenoid distance, and anterior glottic angle. RESULTS: Eighteen patients were included in the study. Three patients were tracheostomy-dependent and were successfully decannulated. All other cases presented short and long-term significant improvement of their dyspnea index score (P < 0.001) in correlation with glottic area enlargement (P < 0.001). There was no statistical difference between preoperative and postoperative voice and swallowing parameters. CONCLUSION: Our transoral lateralization technique allows enlargement of the glottic aperture in case of laryngeal dyspnea secondary to vocal fold paralysis in adduction. This technique optimally preserves laryngeal structures, especially the mucosa. It is reproducible and reliable for all laryngologists experienced in reconstructive transoral laser microsurgery.

Mechanics of human vocal folds layers during finite strains in tension, compression and shear.

During phonation, human vocal fold tissues are subjected to combined tension, compression and shear loading modes from small to large finite strains. Their mechanical behaviour is however still not well understood. Herein, we complete the existing mechanical database of these soft tissues, by characterising, for the first time, the cyclic and finite strains behaviour of the lamina propria and vocalis layers under these loading modes. To minimise the inter or intra-individual variability, particular attention was paid to subject each tissue sample successively to the three loadings. A non-linear mechanical behaviour is observed for all loading modes: a J-shape strain stiffening in longitudinal tension and transverse compression, albeit far less pronounced in shear, stress accommodation and stress hysteresis whatever the loading mode. In addition, recorded stress levels during longitudinal tension are much higher for the lamina propria than for the vocalis. Conversely, the responses of the lamina propria and the vocalis in transverse compression as well as transverse and longitudinal shears are of the same orders of magnitude. We also highlight the strain rate sensitivity of the tissues, as well as their anisotropic properties.

Changes in the voice production of solo singers across concert halls.

To investigate the influence of room acoustics on singing, four lyrical singers (soprano, mezzo-soprano, tenor, baritone) performed four musical pieces in eight different venues (from dry studio to reverberant church). In addition to vocal intensity measured by a near-field microphone, glottal behavior (vibratory fundamental frequency and contact quotient) was assessed by electroglottography. Statistical linear mixed models showed that the variance in vocal performance was partly explained by room acoustics. Complementary to previous results on voice musical features influenced by timbre and level of the room's response, voice production parameters were mostly influenced by spatial aspects of the room's response.

Vocal Fundamental Frequency and Sound Pressure Level in Charismatic Speech: A Cross-Gender and -Language Study.

OBJECTIVES/HYPOTHESES: Charismatic leaders use vocal behavior to persuade their audience, achieve goals, arouse emotional states, and convey personality traits and leadership status. This study investigates voice fundamental frequency (f0) and sound pressure level (SPL) in female and male French, Italian, Brazilian, and American politicians to determine which acoustic parameters are related to cross-gender and cross-cultural common vocal abilities, and which derive from culture-, gender-, and language-specific vocal strategies used to adapt vocal behavior to listeners' culture-related expectations. STUDY DESIGN: Speech corpora were collected for two formal communicative contexts (leaders address followers or other leaders) and one informal communicative context (dyadic interaction), based on the persuasive goals inherent in each context and on the relative status of the listeners and speakers. Leaders' acoustic voice profiles were created to show differences in f0 and SPL manipulation with respect to speakers' gender and language in each communicative context. RESULTS: Cross-gender and cross-language similarities in manipulation of average f0 and in f0 and SPL ranges occurred in all communicative contexts. Patterns of f0 manipulation were shared across genders and cultures, suggesting this dimension might be biologically based and is exploited by leaders to convey dominance. Ranges for f0 and SPL seemed to be affected by the communicative context, being wider or narrower depending on the persuasive goal. Results also showed language- and speaker-specific differences in the acoustic manipulation of f0 and SPL over time. CONCLUSIONS: These findings are consistent with the idea that specific charismatic leaders' vocal behaviors depend on a fine combination of vocal abilities that are shared across cultures and genders, combined with culturally- and linguistically-filtered vocal strategies.

3D multiscale imaging of human vocal folds using synchrotron X-ray microtomography in phase retrieval mode.

Human vocal folds possess outstanding abilities to endure large, reversible deformations and to vibrate up to more than thousand cycles per second. This unique performance mainly results from their complex specific 3D and multiscale structure, which is very difficult to investigate experimentally and still presents challenges using either confocal microscopy, MRI or X-ray microtomography in absorption mode. To circumvent these difficulties, we used high-resolution synchrotron X-ray microtomography with phase retrieval and report the first ex vivo 3D images of human vocal-fold tissues at multiple scales. Various relevant descriptors of structure were extracted from the images: geometry of vocal folds at rest or in a stretched phonatory-like position, shape and size of their layered fibrous architectures, orientation, shape and size of the muscle fibres as well as the set of collagen and elastin fibre bundles constituting these layers. The developed methodology opens a promising insight into voice biomechanics, which will allow further assessment of the micromechanics of the vocal folds and their vibratory properties. This will then provide valuable guidelines for the design of new mimetic biomaterials for the next generation of artificial larynges.

Vocal tract resonances in singing: variation with laryngeal mechanism for male operatic singers in chest and falsetto registers.

Seven male operatic singers sang the same notes and vowels in their chest and their falsetto registers, covering the overlap frequency range where two main laryngeal mechanisms can be identified by means of electroglottography: M1 in chest register and M2 in falsetto register. Glottal contact quotients determined using electroglottography were typically lower by 0.27 in M2 than in M1. Vocal tract resonance frequencies were measured by using broadband excitation at the lips and found to be typically lower in M2 than in M1 sung at the same pitch and vowel; R1 typically by 65 Hz and R2 by 90 Hz. These shifts in tract resonances were only weakly correlated with the changes in the contact quotient or laryngeal height that were measured simultaneously. There was considerable variability in the resonance tuning strategies used by the singers, and no evidence of a uniform systematic tuning strategy used by all singers. A simple model estimates that the shifts in resonance frequencies are consistent with the effective glottal area in falsetto register (M2) being 60%-70% of its value in chest register (M1).