Assessing Fundamental Frequency Variation in Speakers With Parkinson's Disease: Effects of Tracking Errors

Abstract

Purpose: Automatic measurements of fundamental frequency ( F 0) typically contain tracking errors that can be challenging to accurately correct. This study assessed to what degree these errors change F 0 summary statistics in speakers with Parkinson's disease (PD) and neurotypical adults. In addition, we include a case study examining how the removal of tracking errors influenced our ability to predict a perceptual outcome measure, speech expressiveness, associated with dysarthria and PD. Several different statistical approaches for characterizing F 0 variability were used to demonstrate the influence of tracking errors. Method: Eight speakers with PD and eight neurotypical speakers were recorded reading The Caterpillar passage. F 0 measurements were extracted in Praat and tracking errors were manually identified. The effect of tracking errors on F 0 mean and standard deviation was statistically analyzed. Twenty listeners rated speech expressiveness across 80 sentences. The relationship between listener ratings and F 0 variability was examined using different statistical approaches for characterizing F 0 variability (with and without tracking errors). Results: Measurements of F 0 standard deviation, but not F 0 mean, were significantly affected by tracking errors. Relationships between measurements of F 0 variability and expressiveness were strengthened when tracking errors were removed from data analysis. Conclusions: Tracking errors significantly alter F 0 standard deviation values for both speakers with PD and neurotypical adults. Case study evidence also suggests that tracking errors can reduce the strength of relationships between F 0 variability and perceptual outcome measures, such as speech expressiveness.