Speech characterization and synthesis by nonlinear methods

This paper addresses recent suggestions in the literature that the generation of speech is a nonlinear process. This has sparked great interest in the area of nonlinear analysis of speech with a number of studies being conducted to investigate whether low dimensional chaotic attractors exist for speech, This paper examines a corpus of sustained vowel sounds which were recorded for this study to ensure dynamical invariance. The sounds are assessed by a range of the invariant geometric features developed for the analysis of chaotic systems such as correlation dimension, Lyapunov exponents, and short-term predictability. The results presented suggest that although voiced speech is well characterized by a small number of dimensions, it is not necessarily chaotic, Finally, a synthesis technique for voiced sounds is developed inspired by the technique for estimating the Lyapunov exponents.