The heart sound de-noising method based on the wavelet packet and local noise estimation

Heart sound is a kind of typical non-stationary weak signal. Heart sounds from clinical settings are unavoidably contaminated by some noise. The noise in heart sounds includes colored noise and white noise. A de-noising method is presented in this paper, which is based on a harmonic wavelet packet and adopts the methods of finding an optimal decomposing under the minimum entropy principle, selecting reasonable decomposing depths and estimating the local noise as de-noising thresholds. The experiment results show that the method is effective.