Quantifying correlations in pitch- and amplitude contours of sustained phonation

Nonlinear phenomena such as subharmonics, biphonation, or deterministic cha os induce characteristic patterns in pitch- and amplitude contours. We intr oduce a novel measure of correlations in contours termed MAC (Mean Average Correlation). For uncorrelated and weakly correlated noise the Values of MA C are calculated, and they turn out to be rather small. Moreover, we analyz e simulations of the circle map and find high values of MAC for subharmonic and chaotic data. We present examples of severely rough voices where corre lations in contours are quantified by MAC. Finally, we study the connection between perceived voice quality and MAC with the aid of 120 perceptually e valuated voices.