Irregularity of vocal period and amplitude: A first approach to the fractal analysis of voice

Fractal geometry, a relatively young branch of mathematics, offers new ways of evaluating the irregularity of the physiologic and acoustic aspects of speech. The validity and reliability of a box-counting method for estimating the fractal dimension (D_F) of the period and amplitude of vocal signals were demonstrated, and the method was applied to sustained vowels produced by four men and four women. Mean D_F of the fundamental period was 1.46; D_F of the amplitude records averaged a slightly, but significantly, higher 1.54. The potential of D_F as a research and clinical tool is considered.