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Heart sound is one of the most important physiological signals in body. But due to its complexity and other factors it contains a lot of noise. In order to analyze heart sound signals better the de-noising is integrant. In this paper the wavelet de-noising method based on three thresholding functions is used for heart sound signals de-noising, soft-thresholding and hard-thresholding functions are traditional, and an improved novel thresholding function with double variables parameters is novel. The critical point of the wavelet de-nosing of signals is the choice of thresholds and thresholding functions. The novel thresholding function can give different results only by changing the values of variable parameters. It can overcome the shortcoming discontinuous function in hard-thresholding function, and also can eliminate the permanent bias in soft-thresholding function. The simulation result indicates that the new thresholding function can get better SNR gains. The experiments show that it is more predominant than the classical soft-thresholding and hard-thresholding function for heart sound signals de-noising.