Nonlinear Dynamic Analysis and Perturbation Measurement Used for Discriminating Pathological Voices and Their Correlations With Perceptual Evaluation.

OBJECTIVE: 1. To investigate the discriminatory and diagnostic power of nonlinear dynamic analysis measures concerning voices from normal, benign, and malignant voice disorders. 2. To study the correlations of nonlinear dynamic analysis measures with perceptual ratings to evaluate the reliability of the objective acoustic analysis in predicting severity of voice. METHOD: The perturbation analysis metrics used were Jitter%, Shimmer%, and signal-to-noise ratio. The nonlinear dynamic analysis metrics used were spectrum convergence ratio (SCR), nonlinear energy difference ratio (NEDR), and rate of divergence (ROD). Subjects were enrolled and divided into three groups based on laryngeal pathology: normal, benign, and malignant. Vowel sound and reading samples were recorded. Perceptual evaluation was applied to these voice samples to investigate correlations between metrics and auditory perception. RESULT: Each metric was capable of discriminating laryngeal pathology, except for SCR in the case of distinguishing between benign and malignant pathologies. Perturbation analysis parameters had a moderate ability to differentiate between normal and benign pathologies, but were unable to characterize malignant pathologies for certain diseases, such as Reinke's edema. All metrics significantly correlated with perceptual G scores. Nonlinear dynamic analysis was superior when applied to cases of severe dysphonia, where linear metrics such as Jitter% and Shimmer% tended to lose utility. NEDR and ROD were successful at differentiating between the different pathologies, whereas SCR could not discriminate between the benign and malignant groups. CONCLUSION: Perturbation and nonlinear dynamic analyses are comparable in their discriminating power with respect to normal and benign voices, and normal and malignant voices. The nonlinear dynamic analysis metrics NEDR and ROD may be superior in clinical settings with respect to discriminating voice pathology ranging from mild pathological voice to severe dysphonia, and with respect to discriminating benign and malignant voice. SCR was found unable to discriminate pathological voices.

Optimizing Aerodynamic Vocal Parameters by Varying Supraglottic Pressure Using "Controlled Supraglottic Pressure Phonation" in Healthy Subjects.

OBJECTIVE: The objective of this study is to introduce a novel method for semi-occluded vocal tract (SOVT) therapy called "controlled supraglottic pressure phonation," determine the mechanism by which supraglottic pressure contributes to lowering impedance during SOVT therapy, and provide the optimal supraglottic pressure range for SOVT exercises. METHODS: Twenty-five human subjects were assigned to one of five supraglottic pressure levels, 0, 2, 4, 6, and 8 cmH2O, which were controlled through a continuous positive airway pressure device. Subjects were asked to phonate during both a short- and long-duration task, in which vocal properties were measured before and after. At the end of each task, the subjects reported the levels of discomfort and phonation difficulty on a 0-10 scale to assess the subjective improvement of vocal economy. RESULTS: Significant differences were observed between pre- and post-task measurements for phonation threshold pressure for both the short-duration and long-duration tasks. Phonation threshold flow and frequency measurements were found to have no statistically significant differences. The subjective measures showed elevated discomfort in the higher pressure inputs for both tasks relative to no air. CONCLUSION: Higher supraglottic pressure levels will improve ease of phonation, but the treatment discomfort needs to be considered as well, yielding an optimal supraglottic pressure range of 4-6 cmH2O. "Controlled supraglottic pressure phonation" serves as an alternative to straw phonation that may produce additional benefits.

The Influence of Voice Training on Vocal Learner's Objective Acoustic Voice Components.

OBJECTIVE: Acoustic parameters of voice were studied in music majors throughout 18 months of training to understand the influence of voice training on voice. METHODS: Twenty-three students from Xiamen Music School between 12 and 15 years old were enrolled. Acoustic examination was performed three times- every 6 months for 18 months. Various traditional acoustic parameters were measured, including dysphonia severity index (DSI), jitter, and D-value of vocal range. Nonlinear dynamic measures were also measured, including diffusive chaos to construct voice type component profiles (VTCPs), spectrum convergence ratio, and nonlinear energy difference ratio. The results were analyzed by multivariate analysis of variance. RESULTS: Over the study duration, there was an improvement of DSI (P = 0.002), and D-value of vocal range (P = 0.000). Among nonlinear parameters, only voice type component data demonstrated significant changes during the study duration. Both Voice Type Component 1(VTC1) and VTC3 values differed from Time 1 to Time 2 as well as from Time 1 to Time 3. The proportion of VTC1 in samples generally decreased, while VTC3, representative of aperiodicity, increased. Both nonlinear energy difference ratio and spectrum convergence ratio exhibited no significant changes throughout the study. CONCLUSION: Professional voice training can improve DSI and D-value of vocal range in singers' voices. These parameters have potential to be used for voice training evaluation and screening. Many nonlinear parameters did not detect differences in the healthy voices studied, but VTCPs created using intrinsic dimension present a valuable new method, visualizing increases in aperiodicity of the speaking voices after professional voice training.

The Influence of Voice Training on Vocal Learners' Supraglottal Activities and Aerodynamic Evaluation.

OBJECTIVE: Among music majors with only 18 months of training, supraglottal activities and aerodynamic parameters were studied to facilitate understanding of the influence of voice training on characteristics of voice production. METHODS: Twenty-three students at the Xiamen Music School were examined over the course of 18 months of singing training. Only 17 students completed all data collection sessions. All students had no previous voice training and were confirmed to be without organic voice disorders by a laryngologist but did present with supraglottal compression. Strobolaryngoscopy and aerodynamic assessment were performed every 6 months. Using the laryngoscopic images, anterior-posterior (A-P) compression and medial-lateral compression were analyzed. Aerodynamic assessment was carried out to measure maximum phonation time, phonation threshold flow, glottal resistance, subglottal pressure, phonation threshold pressure, and vocal efficiency. From these measurements, the mean was calculated along with a measurement of reliability. One-way ANOVA with Bonferroni post hoc test was used to evaluate the results between subjects at different time points. Kendall's W test was completed to assure consistency between and within laryngologists. RESULTS: Referring to the Strobolaryngoscopy Evaluation Rating Form, 4 of the 17 students had decreased A-P compression scores in the second measurement compared to the first (from 2.24 ± 0.20 to 2.12 ± 0.17, P = 0.100). After completion of the program, 6 of the 17 students' anterior-posterior compression scores further improved from the second measurement (from 2.12 ± 0.17 to 1.71 ± 0.17, P = 0.600). The A-P compression scores showed a gradual downward trend and was overall statistically significant (P = 0.004). In addition, there was an improvement of maximum phonation time (P​ ​= 0.016). CONCLUSION: Professional voice training can improve the supraglottal activities and maximum phonation time. These parameters have potential to be used for voice training evaluation and screening.

Evaluation of Diffusional Characteristics and Microstructure in Unilateral Vocal Fold Paralysis Using Diffusion Tensor Imaging.

OBJECTIVE: To investigate the value of diffusion tensor imaging (DTI) in the evaluation of vocal fold tissue microstructure after recurrent laryngeal nerve (RLN) injury. METHODS: Six canines were divided into 2 groups: a unilateral vocal fold paralysis group (n = 4) and a control group (n = 2). The RLN was cut in the unilateral vocal fold paralysis group, and no intervention was applied in the control group. After 4 months, the canines' larynges were removed and placed in a small animal magnetic resonance imaging (MRI) system (9.4T BioSpec MRI; Bruker, Germany). After scanning, the vocal folds were isolated, sectioned, and stained. The slides were then analyzed for the cross-sectional area and muscle fiber density through feature extraction technology. Pearson correlation analysis was performed on the DTI scan and histological section extraction results. RESULTS: In the vocal fold muscle layer, the fractional anisotropy (FA) of the unilateral RLN injury group was higher than that of the control group, and the Tensor Trace was lower than that of the control group. This difference was statistically significant, P < .05. In the lamina propria, the FA of the unilateral RLN injury group was lower than that of the control group, P > .05, and the Tensor Trace was lower than that of the control group, P < .05. The muscle fiber cross-sectional area of the RLN injury group was significantly smaller than the control group with statistical significance, P < .05, and the density of muscle fibers was lower, P < .05. The correlation coefficient between FA and the cross-sectional area was -0.838, P = .002, and .726; P = .017 between Tensor Trace and the cross-sectional area. CONCLUSION: Diffusion tensor imaging is an effective method to assess the changes in the microstructure of atrophic vocal fold muscle tissue after RLN injury.