Examining the Conversational Speech Intelligibility of Individuals with Hypophonia Associated with Parkinson's Disease

Compromised speech intelligibility often is a consequence of hypokinetic dysarthria associated with Parkinson's disease (PD) (Adams, Dykstra, Jenkins, & Jog, 2008). A relatively unexplored area of research is the evaluation of conversational intelligibility in speakers with hypophonia as a primary speech symptom. Evidence suggests that hypophonia may be most evident during conversational speech tasks (Adams, Dykstra, Abrams, Winnell, Jenkins, & Jog, 2006a). This study evaluated the impact of background noise on the conversational speech intelligibility of control participants and those with hypophonia associated with PD. Thirty individuals with hypophonia and PD and 15 healthy control participants participated in conversation with various levels of background noise. Results revealed nonsignificant differences between groups when conversational intelligibility was assessed in a no background noise condition. Significant results were found when conversational intelligibility was assessed in the presence of three intensity levels of background noise. The results of this study demonstrate that participants with hypophonia have significant deficits in conversational speech intelligibility even in relatively low levels of background noise. Furthermore, deficits in speech intelligibility are exacerbated with increasing levels of background noise. Assessing speech intelligibility using conversational speech tasks that are obtained in different levels of background noise appears to provide an ecologically valid estimate of intelligibility and may be a useful indicator of the disability associated with hypophonia in PD.