利用窗函数法设计FIR滤波器，绘制出滤波器的特性图。利用所设计的滤波器对多个频带叠加的正弦信号进行处理，对比滤波前后的信号时域和频域图，验证滤波器的效果。最后录制或下载一段语音信号，对其进行采样和加噪，然后用设计滤波器对加噪后信号进行滤波，绘制出信号的时域波形和频谱，分别计算均值、方差、自相关函数、功率谱，并对滤波前后的信号进行对比。(Using window function design FIR filter, draw the filter characteristic diagram. The designed filter is used to process the sinusoidal signals superimposed on several frequency bands, and the time domain and frequency domain signals are compared before and after filtering to verify the effect of the filter. The final recording or download a voice signal, the sampling and noise, then the noise signal is filtered by the filter design, draw time-domain signal waveform and spectrum, mean, variance, autocorrelation function and power spectrum were calculated and compared before and after filtering the signal.)