In this study, the Fourier transform, wavelet transform and turbulence filter methods have been applied to coaxial jet flows for various downstream positions in the inner and outer mixing regions. The data were obtained from cross-wire measurements,so axial and radial velocity components were acquired. Attention is focused on the characteristics of these signals in the initial region of the jet-flow field. The effects of some basic mechanisms of the vorticity dynamics on the velocity time histories, and on different statistical and spectral quantities, are studied. (C) 2000 Academic Press.