Measurement of voice onset time in dysarthric patients: methodological considerations

Voice onset time (VOT) reflects the timing control between laryngeal and supralaryngeal adjustments. It has been studied both in normal speakers and patients with speech disorders, but very little information has been published on the feasibility of this measure in clinical practice. We examined 10 repeated utterances involving the voiceless stop consonants [p], [t] and [k] in 110 subjects (27 controls, 48 with spastic dysarthria and 35 with hypokinetic dysarthria). The mean rate of measurable VOT was 95% for normal speech, 80% for hypokinetic dysarthria and 84% for spastic dysarthria. The main obstacle to successful measurement was lack of the burst signifying the release of the plosive. The posterior stop [k] presented the greatest measurement difficulties for the dysarthric subjects, which is in accordance with previous perceptual reports on dysarthria.