Loudness Matching in Individuals with Parkinson’s Disease and Hypophonia
Abstract
The purpose of the present study was to investigate speech loudness perception in 15 individuals with Parkinson’s disease (IWPD) and hypophonia (reduced speech intensity) and 15 healthy control (HC) participants. A loudness matching procedure was used to examine conditions involving speech loudness targets presented at various levels (60 to 80dB SPL). The loudness response conditions included manually controlled audio playback of external speech, self-vocalized speech, amplified self-speech, and speech projected to a distance of 2 meters. For most of the loudness matching conditions, the PD group did not demonstrate the predicted deficit in loudness matching. In some loudness matching conditions, the PD group had lower (more accurate) error scores than the HC group. More specifically, for most of the loudness matching conditions involving self-vocalized (imitation) responses, the PD group had significantly lower error scores than the HC group. This result is inconsistent with previous studies of speech loudness imitation in PD. In addition, the finding that a PD group had better performance than a HC group is judged to be unique in the field of speech perception and production. Factors that may have influenced these results include the ordering of experimental conditions, the facilitating effect of a preceding limb motor task, hypophonia symptom severity, and PD-related enhancement of feedback processes. Future studies are required to replicate and further examine these speech loudness matching results in IWPD and hypophonia.