Glottic area during vocalisation.

<p>A. A representative subject. The shaded area, removed in pre-processing, corresponds to a variable time before the subject has begun vocalising. B. Relationship between glottic area (<i>ga</i>) and inter-arytenoid distance (<i>iad</i>) and C. Graphical representation. Arytenoid movement may be described as a circle centred at the anterior commissure: the relationship is quadratic. As the inter-arytenoid distance and the angle between the vocal folds increases glottic area also increases. Despite finding smaller inter-arytenoid distance during vocalisation in Parkinson’s disease, we did not find the expected reduction in the glottic area, suggesting the vocal folds are bowed during vocalisation in Parkinson’s disease.