Aerodynamic, acoustic, and perceptual measures of nasality following traumatic brain injury.

Data were obtained from 31 subjects who had incurred a traumatic brain injury (TBI). Two expert listeners judged nasality using direct magnitude estimation with a referent. They rated samples of the first sentence of the Rainbow Passage, played backwards, with all pauses removed. Sensitivity was good for nasalance, velopharyngeal airway resistance, and velopharyngeal orifice area, indicating that these measures would accurately identify an individual as nasal. Specificity was reduced, and was adequate only for nasalance. The reduced specificity was due to a high number of false positives, i.e. perceived nasality in the absence of objective corroboration. Analysis of the false positives revealed that a slow speaking rate could mislead a listener's perception of nasality. Overall, for individuals with dysarthria following TBI, the measure of nasalance may most accurately reflect listener perception of nasality.