Ataxic dysarthria is a speech disorder in which a disturbance of rhythm is one of the main characteristics. Although this feature has been recognised since some time ago, little detail is known on the specific manifestations of this problem. Acoustic analysis of rhythm can go some way towards extending our knowledge in this area, however, insufficient information is available on which measures are best suited to such investigations. Acoustic rhythm metrics have largely been developed for cross-linguistic comparisons of unimpaired speakers, and further research needs to be performed to identify the most suitable methodology for the evaluation of disordered speech. This study contributes to filling this knowledge gap by investigating the rhythmic differences between (cerebellar) ataxic dysarthric speech and normal speech with a range of analysis methods and speech tasks, with the aim to identify which acoustic rhythm metric is most suited to differentiate disordered from healthy speech performance, which task(s) can highlight such differences most, and which rhythm metrics correlates best with perceptual evaluations. Different speech samples, ranging from structured to unstructured, from six speakers with ataxic dysarthria and six age and gender matched control speakers were analysed with five different rhythm measures: the normalized Pairwise Variability Index (nPVI), the VarcoV, the Proportion of Vocalic Intervals (%V), the Variability Index (VI), and the Interstress Interval measure (ISI). The results of the acoustic analysis were compared with a perceptual evaluation of the participants' speech. Results varied between different rhythm metrics and speech tasks, but nPVI and VarcoV seem to be the metrics most suitable to characterize rhythmic changes in ataxic dysarthria. These two yielded significant differences between the ataxic dysarthric and control group, and furthermore correlated significantly with the perceptual evaluation of rhythm. However, the VarcoV and nPVI (as well as the %V) metric also correlated significantly with articulation rate and future research will need to investigate further the impact this can have on rhythmic analysis in disordered speakers. In relation to task choice, the results indicate that spontaneous speech samples are a suitable task to highlight rhythmic disturbances.
|Date of Award||7 May 2015|
- University Of Strathclyde
|Supervisor||Anja Lowit (Supervisor)|