1. A method of processing a cardiovascular physiological signal, comprising: decomposing the cardiovascular physiological signal into a first plurality of wavelet coefficients using a wavelet transform; selecting a second plurality of wavelet coefficients from the first plurality of wavelet coefficients, the second plurality being a subset of the first plurality; classifying or clustering the cardiovascular physiological signal into one of a plurality of predetermined classes based on the second plurality of wavelet coefficients using an artificial neural network; and computing a regularized variance of each of the first plurality of wavelet coefficients, wherein the second plurality of wavelet coefficients are selected based on the regularized variance.