Dissertation Defense Announcement
School of Communication Sciences and Disorders announces the Final Dissertation Defense of
for the Degree of Doctor of Philosophy
June 27, 2018 at 10:00 AM in School of Communication Sciences & Disorders, Dean's Conference Room 3017H
Advisor: Eugene H. Buder
Spectral/Cepstral Analysis of Voice Quality in Patients with Parkinson's Disease
ABSTRACT: The purpose of this dissertation was to determine whether voice quality improves in speakers with idiopathic Parkinson's Disease (PD) as a result of Lee Silverman Voice Treatment (LSVT). As demonstrated, LSVT has shown an effect on voice intensity. However, few acoustical studies have been done to investigate the effects of LSVT on voice quality. Therefore, there is a need to strengthen the database on the acoustical effects of LSVT on voice quality. The first study (Chapter 2) investigated the cepstral/spectral analyses of sustained /ɑ/ vowels produced by speakers with idiopathic Parkinson's Disease before and after LSVT and found in addition to the increased intensity, PD speakers exhibited both improved harmonic structure and voice quality as reflected in cepstral/spectral measures. These findings indicated that LSVT did have an overall beneficial effect on voice quality in sustained vowels. Thus, the first study extends the previous findings supporting the use of cepstral peak prominence (CPP), CPP Standard Deviation (CPP-SD), and Cepstral/Spectral Index of Dysphonia (CSID) (KayPENTAX, 2011) as treatment outcome measures for documenting phonatory changes before and after LSVT in PD speakers. It was of interest to know whether to evaluate PD voice quality in sustained phonation or connected speech because this will clarify the best assessment protocols for verifying treatment outcomes. Thus, the second study (Chapter 3) investigated individual differences in continuous speech versus sustained vowel to understand changes that occurs in voice quality as a response to LSVT in PD speakers. The results demonstrated that only CPP work with connected speech significantly at the group level. Individual differences demonstrated that only four subjects improved following treatment in CPP, CPP-SD, and CSID in both sustained phonation and connected speech. Only three of them showed a reduction in L/H SR and L/H SR SD in sustained phonation and only one showed an increase in L/H SR and L/H SR SD in connected speech. The other subjects varied in terms of their improvement but the majority demonstrated voice quality improvement in sustained phonation. The results demonstrated that sustained phonation was better than connected speech to demonstrate voice quality improvement following treatment.