在小波的分解过程中，每一次的小波分解得到的近似信号会比上一层次的信号更加光滑，而被抑制的细节系数则存在于每一层中。所以可以将一个含噪信号进行第5层分解，并有选择的抑制部分细节系数就可以达到信号降噪的目的。试验中采用‘db4’小波对信号进行分解。-In the process of wavelet decomposition, every wavelet decomposition to get the approximate signals will be more smooth than on a level of signal, and inhibited detail coefficients exist in each layer. So a noise signal can be 5 layers of decomposition, and selectively inhibit some detail coefficients can achieve the goal of signal noise reduction. Trials of the signal by　db3 wavelet decomposition.