Electronic Thesis and Dissertation Repository


Master of Science


Health and Rehabilitation Sciences


Dr. Allyson Dykstra


Reduced speech intensity or hypophonia is a common speech deficit observed in hypokinetic dysarthria associated with Parkinson’s disease (PD). The introduction of background noise is a particularly relevant context to study in relation to this speech symptom. Previous research has indicated that listeners have more difficulty understanding dysarthric speech, and must exert more effort when listening. However, little is known of the specific features of the speech signal that contribute to perceived listener effort in the speech of individuals with PD and hypophonia. The purpose of this study is to investigate two speech features (1. Articulatory Imprecision 2. Reduced Loudness) that may contribute to perceived listener effort and that are commonly impaired in individuals with PD. This study also aims to determine potential relationships among ratings of listener effort and speech intelligibility in two noise conditions (no added background noise and 65 dB multi-talker background noise). Listener participants orthographically transcribed audio recordings of each speaker with PD reading three sentences from the Sentence Intelligibility Test (SIT). Intelligibility, listener effort, articulatory imprecision, and reduced loudness of these sentences was also rated in each noise condition using visual analogue scaling (VAS). Results revealed that the noise condition had a significant impact on the ratings of intelligibility, listener effort, articulatory imprecision, and reduced loudness. The results of this study revealed that individuals with PD and hypophonia were rated to have less intense speech, less precise speech, and reduced speech intelligibility in background noise, and ratings of listener effort were also significantly higher in background noise.