Acoustic analysis of the tremulous voice: Assessing the utility of the correlation dimension and perturbation parameters

Acoustic analysis may provide a useful means to quantitatively characterize the tremulous voice. Signals were obtained from 25 subjects with diagnoses of either Parkinson's disease or vocal polyps exhibiting vocal tremor. These were compared to signals from 24 subjects with normal voices. Signals were analyzed via correlation dimension and several parameters from the Multi-Dimensional Voice Program (MDVP): percent jitter, percent shimmer, amplitude tremor intensity index (ATRI), frequency tremor intensity index (FTRI), amplitude tremor frequency (Fatr), and fundamental frequency tremor frequency (Fftr). No significant difference was found between the tremor and control groups for ATRI and Fatr. Percent jitter, percent shimmer, FTRI, Fftr, and correlation dimension values were found to be significantly higher in the tremor group than in the control group. We conclude that these parameters may have utility for the clinical quantification of tremor severity and treatment effects. Learning Outcomes: The reader will understand the utility of applying select perturbation parameters and the nonlinear measure of correlation dimension for the characterization of the tremulous voice. (C) 2009 Elsevier Inc. All rights reserved.