Acoustical analysis of voices produced by Cantonese patients of unilateral vocal fold paralysis acoustical analysis of voices by Cantonese UVFP

Injection laryngoplasty using hyaluronic acid for patients of unilateral vocal fold paralysis (UVFP) is becoming more prevalent in Hong Kong. The present investigation explored the efficacy of the procedure by examining various acoustical measures. Both traditional perturbation analyses and nonlinear dynamical measures were used to assess the change in patients´ voice quality between before, one month and three months after injection laryngoplasty. Jitter, shimmer, noise-to-harmonic ratio (NHR), and nonlinear recurrence period density entropy (RPDE), detrended fluctuation analysis (DFA) and correlation dimension (D₂) were obtained from the sustained vowel /i/ produced by ten native Cantonese UVFP patients. Results showed that RPDE and D₂ were sensitive to improvement after injection laryngoplasty. The receiver operating characteristic area under curve analysis (ROC-AUC) was also used to demonstrate the diagnostic performance of these objective measures. High specificity of these four acoustic measures in distinguishing the voice quality before and after surgery was found, indicating that nonlinear dynamical analysis could be a supplemental tool to traditional acoustic analysis, and if combined, an effective monitoring tool for UVFP treatment.