Voicing status of word final plosives in Friedreich's Ataxia dysarthria

In a previous study, the authors identified final plosive voicing contrast as the highest single error source in dysarthria associated with Friedreich's Ataxia in a group of Irish English-speaking participants. This study aimed to determine the acoustic features underlying misperceptions of voicing status and implications for clinical management. Words with final plosives were extracted from recordings of ten speakers with Friedreich's Ataxia. Various measures of the syllable rhyme were compared with intelligibility scores. Vowel duration, voicing in the closure, F1 frequency at mid-vowel and a drop in F1 at vowel termination accounted for 58% of the variance in the relevant intelligibility scores, with vowel duration being most heavily implicated. While inappropriate vowel duration is the factor most likely to lead to misperceptions of final plosive voicing status, other factors may overcome its effect. Therapeutic intervention with this population should be based on a comparison of intelligibility assessment with acoustic measurement.