An asymmetric smooth contour two-mass model for recurrent laryngeal nerve paralysis

Asymmetric triangular body-cover model of the VFs with bilateral intrinsic muscle activation

Many voice disorders are linked to imbalanced muscle activity and known to exhibit asymmetric vocal fold vibration. However, the relation between imbalanced muscle activation and asymmetric vocal fold vibration is not well understood. This study introduces an asymmetric triangular body-cover model of the vocal folds, controlled by the activation of intrinsic laryngeal muscles, to investigate the effects of muscle imbalance on vocal fold oscillation. Various scenarios were considered, encompassing imbalance in individual muscles and muscle pairs, as well as accounting for asymmetry in lumped element parameters. The results highlight the antagonistic effect between the thyroarytenoid and cricothyroid muscles on the elastic and mass components of the vocal folds, as well as the impact on the vocal process from the imbalance in the lateral cricoarytenoid and interarytenoid adductor muscles. Measurements of amplitude and phase asymmetry were employed to emulate the oscillatory behavior of two pathological cases: unilateral paralysis and muscle tension dysphonia. The resulting simulations exhibit muscle imbalance consistent with expectations in the composition of these voice disorders, yielding asymmetries exceeding 30% for paralysis and below 5% for dysphonia. This underscores the versatility of muscle imbalance in representing phonatory scenarios and its potential for characterizing asymmetry in vocal fold vibration.

ROC Analysis Cut-off Points of Hellenic Voice Handicap Index for Neurogenic Voice Disorders Patients: an Exploratory Study

OBJECTIVE

The inclusion of subjective methods for evaluating Voice Disorders is proven an essential factor for diagnosis as these methods include self-reported questionnaires (eg, Voice Handicap Index-VHI) for everyday clinical practice. In turn, by obtaining cut-off scores of self-perceived questionnaires intended for assessment procedures of different voice disorders (eg, patients with neurological problems), the clinicians might be helped toward finding their patients' needs leading to better monitoring, and treatment suggestions. Consequently, the purpose of this study was to estimate the cut-off scores for the Greek VHI relevant to patients with neurogenic voice disorders.

METHODS

Ninety subjects participated in this research. Sixty-six of them served as the control group while the remaining 24 patients exhibited Neurogenic Voice Disorders (eg, spasmodic dysphonia or vocal fold paralysis). They filled in the VHI and the Voice Evaluation Template. All participants were examined with the use of video laryngeal endoscopy and stroboscopy.

RESULTS

The analysis revealed higher medians in all domains (of the VHI) for the patients compared to the control group. The cut-off points were estimated at the values of 24.50 (Total Score-AUC 0.932, P = 0.000), 9.00 (Functional Domain-AUC 0.917, P = 0.000), 10.00 (Physical Domain-AUC 0.948, P = 0.000), and 9.00 (Emotional Domain-AUC 0.830, P = 0.000).

CONCLUSION

The estimated cut-off scores are in agreement with previous studies. These scores could probably used to enhance therapeutic monitoring of patients who suffer from neurogenic voice disorders. This study underlines the importance of considering different cutoff points for individuals with voice disorders due to diverse neurogenic etiologies.

Sensitivity analysis of muscle mechanics-based voice simulator to determine gender-specific speech characteristics

The purpose of this study was to investigate the gender differences in voice simulation using a sensitivity analysis approach. A global, Monte Carlo-based approach was employed, and the relationships between biomechanical inputs (lung pressure and muscle activation levels) and acoustic outputs (fundamental frequency, f₀, and sound pressure level, SPL) were investigated for male and female versions of a voice simulator model. The gender distinction in the model was based on an anatomical scaling of the laryngeal structures. Results showed strong relationships for f₀ and SPL as functions of lung pressure, as well as for f₀ as a function of cricothyroid and thyroarytenoid muscle activity, in agreement with previous literature. Also expected was a systematic shift in f₀ range between the genders. It was found that the female model exhibited greater pitch strength (saliency) than the male model, which might equate to a perceptually more periodic or higher-quality voice for females. In addition, the female model required slightly higher lung pressures than the male model to achieve the same SPL, suggesting a possibly greater phonatory effort and predisposition for fatigue in the female voice. The methods and results of this study lay the groundwork for a complete mapping of simulator sound signal characteristics as a function of simulator input parameters and a better understanding of gender-specific voice production and vocal health.

Corrected contact dynamics for the Steinecke and Herzel asymmetric two-mass model of the vocal folds

The simplified two-mass model of human vocal folds, proposed by Steinecke and Herzel [J. Acoust. Soc. Am. 97(3), 1874-1884 (1995)], has seen widespread use throughout the speech community. Herein, an error is corrected in the contact loadings on colliding vocal folds with asymmetric tissue properties, as arises clinically in cases of unilateral paralysis. A revised contact model is proposed that remediates the erroneous asymmetric contact forces. The vibration regime map presented in Steinecke and Herzel illustrating the dynamical behavior of the system is revised using the corrected collision model.