Nonlinear dynamical analysis of normal voices

Human voice has been the focus of study for different areas of sciences. Researches in the last two decades have established the existence of chaos in human voice production. The purpose of this paper is to use nonlinear dynamics methods in the analysis of normal voices from healthy subjects and correlate them to traditional acoustic parameters as well as perceptual analysis. Twelve human voice signals from healthy subjects, 6 males and 6 females, ranging in age from 19 to 39 years old were used. Sustained vowel sounds /a/, /e/ and /i/ if, from Brazilian Portuguese were recorded at a sampling rate of 22,050 Hz and analyzed in order to obtain acoustic perturbation measures (jitter, shimmer, coefficient of excess - EX, and pitch amplitude - PA), The phase space reconstruction method was used to describe the nonlinear dynamic characteristics of voice signal samples. This paper shows that nonlinear dynamical methods as phase space reconstruction seems to be a suitable technique for voice signals analysis, due to the chaotic component of the human voice. The results suggest that non-linear dynamic analysis does not replace existing techniques instead they may improve and complement the recent voice analysis methods available for health professionals, speech therapist and clinician.