读入bluesky3.wav文件（内容为男生“蓝天，白云”），在语音数据中混入50Hz的交流声，设计一个用凯泽窗的带组数字滤波器，通带截止评率45Hz,带组截止频率49和51，阻带最小衰减A2=50dB,采样频率为8000Hz(Read the bluesky3.wav file (the content is for boys "blue sky, white clouds"), mix 50Hz hum into the voice data, design a band digital filter with Kaiser window, passband cutoff rate 45Hz, band cutoff Frequency 49 and 51, the minimum attenuation of the stop band is A2=50dB, and the sampling frequency is 8000Hz.)