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

Abstract

Purpose: Automatic measurements of fundamental frequency (F0) typically contain tracking errors that can be challenging to accurately correct. This study assessed to what degree these errors change F0 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 F0 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. F0 measurements were extracted in Praat and tracking errors were manually identified. The effect of tracking errors on F0 mean and standard deviation was statistically analyzed. Twenty listeners rated speech expressiveness across 80 sentences. The relationship between listener ratings and F0 variability was examined using different statistical approaches for characterizing F0 variability (with and without tracking errors).

Results: Measurements of F0 standard deviation, but not F0 mean, were significantly affected by tracking errors. Relationships between measurements of F0 variability and expressiveness were strengthened when tracking errors were removed from data analysis.

Conclusions: Tracking errors significantly alter F0 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 F0 variability and perceptual outcome measures, such as speech expressiveness.