说明：  本程序重构各层低频和高频系数，画功率谱，横坐标为频率，纵坐标为功率，小波包分解最后一句是为显示小波包四层分解树结构
(Reconstruction of the procedural layers of low and high frequency coefficients, draw power spectrum, the abscissa is the frequency, the vertical axis is power, wavelet packet decomposition is the last sentence of four to show the wavelet packet decomposition tree)