Quantification of rhythm problems in disordered speech: a re-evaluation.

Disordered speech can present with rhythmic problems, impacting on an individual's ability to communicate. Effective treatment relies on the availability of sensitive methods to characterize the problem. Rhythm metrics based on segmental durations originally designed for cross-linguistic research have the potential to provide such information. However, these measures may be associated with problems that impact on their clinical usefulness. This paper aims to address the perceptual validity of cross-linguistic metrics as indicators of rhythmic disorder. Speakers with dysarthria and matched healthy participants performed a range of tasks, including syllable and sentence repetition and a spontaneous monologue. A range of rhythm metrics as well as clinical measures were applied. Results showed that none of the metrics could differentiate disordered from healthy speakers, despite clear perceptual differences, suggesting that factors beyond segment duration impacted on rhythm perception. The investigation also highlighted a number of areas where caution needs to be exercised in the application of rhythm metrics to disordered speech. The paper concludes that the underlying speech impairment leading to the perceptual and acoustic characterization of rhythmic problems needs to be established through detailed analysis of speech characteristics in order to construct effective treatment plans for individuals with speech disorders.