Loudness perception of pure tones in Parkinson’s disease

Abstract

Previous work has shown evidence for atypical externally and self-generated speech loudness perception in Parkinson’s disease (PD) with variable methods. This study comprehensively examined loudness ratings of pure tones in individuals with PD and healthy controls, controlling for hearing status. Twenty individuals with PD and twenty-three controls rated the loudness of pure tones on a scale from 1, “Very Soft” to 7, “Uncomfortably Loud.” Tones at 500, 750, 1000, 2000, and 4000 Hz were presented from 35 dB HL to 80 dB HL (or until a rating of 7). A mixed-model analysis of variance (ANOVA) was performed on the ratings to assess the effects of group, frequency, sound pressure level, and ear. Mean loudness growth was determined for each group. There were no significant differences in ratings by frequency. A small but significant difference was seen in mean loudness growth: controls had a shallower slope compared to the PD group. Findings suggest that individuals with PD have a steeper growth of loudness of externally generated tones, in contrast with the findings of previous studies of externally generated and self-generated speech. The underlying causes for impaired perception and production of loudness in PD requires further investigation.