About 90% of individuals diagnosed with Parkinson’s disease will experience changes in their speech and voice. These changes are collectively called hypokinetic dysarthria. The symptoms of hypokinetic dysarthria include rough, weak, and breathy vocal quality, monopitch and monoloudness.
“As speech and voice symptoms progress, one’s voice may become very soft and have a gravelly quality to it. However, it is important to keep in mind that everyone with Parkinson’s disease experiences the changes in speech and voice differently and to different degrees of severity,” Convey explains.
In the field of speech-language pathology, perceptual analysis involves ratings completed by a trained clinician. Even though this rating method is accepted as clinical practice, it is biased towards the rater’s clinical experience. To avoid this dilemma, acoustic measures provide objective information on given parameters of the speech signal. Single measures provide information on one parameter of the speech signal, while multiparametric measures provide more complex information. Convey’s dissertation examines the multiparametric measures of Acoustic Voice Quality Index (AVQI) and the Acoustic Breathiness Index (ABI). She analyses the measures in comparison to perceptual analysis completed by expert raters of Parkinson’s disease and the patients’ disease stage.
“This research has been exciting to work on because it was the first time that AVQI and ABI have been applied with Finnish speakers with Parkinson’s disease,” Convey says.
AVQI is a novel software that provides an objective rating of speech intelligibility. This software automates the Vowel Articulation Index computation which, when completed by hand, is subject to human bias. The AVQI index provides an objective rating of voice quality; specifically, this measure distinguishes a dysphonic voice from a healthy one. The ABI index provides an objective rating of breathy vocal quality and distinguishes a breathy from a non-breathy voice.
In Parkinson’s disease, the early speech and voice changes include altered fundamental frequency as well as changes in the prosody of speech and voice quality. Even though these changes cannot be detected perceptually, they can be detected with the use of acoustic measures. In the study, the AVQI and ABI indexes were used to analyse changes in voice quality over an approximately one-year period in speakers with early-stage Parkinson’s disease. Expanding our understanding of early voice quality changes can aid in the development of measures and protocols for detecting and analysing Parkinson’s disease through voice.
Public defence on Friday 27 September
M.Sc. Rachel Convey’s doctoral dissertation in the field of logopedics (speech-language pathology) titled Acoustic Analysis of Speech and Voice Changes in Parkinson’s Disease will be publicly examined at the Faculty of Social Science of Tampere University at 12 o’clock on Friday 27 September. The venue is auditorium K104 in the Linna building, city centre campus, address: Kalevantie 5, 33100 Tampere. The Opponent will be University Lecturer Sofia Holmqvist-Jämsén from the University of Helsinki. The Custos will be Docent Nelly Penttilä from the Faculty of Social Science at Tampere University.