Speech signals can be considered as being generated by mechanical system with inherently nonlinear dynamics. The purpose of this paper is to describe its complexity using the fractal dimension of a variety of spanish voiced sounds (vowels, nasals) and unvoiced sounds (fricatives) In our research, the fractal dimension was computed over recorder signals from a speech spanish database (AHUMADA), using the method suggested by Katz, [1]. In conclusion the fractals measures expand the distinguishing features in characterizing voiced and unvoiced sounds, that leads to better speech recognition performances.