SPECTRAL/CEPSTRAL ANALYSIS OF VOICE QUALITY IN PATIENTS WITH PARKINSONS DISEASE

The purpose of this dissertation was to determine whether Silverman Voice Treatment (LSVT) affects cepstral/spectral measures of voice quality in speakers with idiopathic Parkinsons Disease (PD). The first study investigated the effect of LSVT on cepstral/spectral measures of sustained // vowels to determine whether voice quality improves. Few studies have investigated the effects of LSVT on voice quality using acoustic measures, and none have used cepstral measures. The first study investigated the effect of LSVT on cepstral/spectral analyses of sustained // vowels produced by speakers. Sustained vowels were analyzed for cepstral peak prominence (CPP), CPP Standard Deviation (CPP-SD), Low/High Spectral Ratio (L/H SR), and Cepstral/Spectral Index of Dysphonia (CSID) using the Analysis of Dysphonia in Speech and Voice (ADSV) program. The study found both improved harmonic structure and voice quality as reflected in cepstral/spectral measures. Voice quality in connected speech is important because it is representative of how a typical individual communicates. Thus, the second studys goals were: First, to investigate the effect of LSVT on cepstral/spectral analysis of connected speech; and second, to compare cepstral/spectral analyses findings in connected speech with findings observed in sustained phonation. Another goal was to examine individual differences in response to treatment and compare them to individual changes observed in sustained phonation. The results demonstrated that CPP increased significantly following LSVT, indicating improved harmonic dominance as a result of treatment, and CSID decreased following LSVT, indicating a reduction of the overall severity in connected speech at the group level. Analysis of individual differences demonstrated that only four participants improved by at least one half Standard Deviation (SD) following treatment in CPP, CPP-SD, and CSID in both sustained phonation and connected speech tasks. Three showed a reduction in L/H SR in sustained phonation and only one showed an increase in L/H SR in connected speech. The other participants improvement varied, but the majority demonstrated voice quality improvement in sustained phonation. The overall results indicated that CPP and CSID were strong acoustic measures for demonstrating voice quality improvement following treatment in both tasks connected speech and sustained phonation