说明：  （1）录制一段语音信号，完成对信号的采样，画出信号的时域波形和频谱图，确定信号的频谱范围； （2）给信号叠加噪声（噪声类型分为如下几种：a白噪声；b单频噪色（正弦干扰）；c多频噪声（多正弦干扰）；d其它干扰。），画出受噪声干扰的信号时域波形和频谱图； （3）采用窗函数法设计FIR低通滤波器，画出滤波器的频响特性图； （4）用所设计的滤波器对受噪声影响的信号进行滤波，画出滤波后语音信号的时域波形图和频谱图； （5）对滤波前后的信号进行对比，分析信号的变化；回放语音信号，并与原始语音信号对比。
((1) record a speech signal, complete the sampling of the signal, draw the time domain waveform and frequency spectrum of the signal, and determine the spectrum range of the signal; (2) signal superposition noise (noise type is divided into the following: a white noise, B single frequency noise (sinusoidal interference); C multifrequency noise (multi sinusoidal interference); d other interference) Noise signal, time domain waveform and spectrogram are drawn; (3) the FIR low-pass filter is designed by using the window function method, and the frequency response characteristic of the filter is drawn; (4) the designed filter is used to filter the signal affected by the noise, and the time domain waveform and spectrogram of the filtered speech signal are drawn; (5) compare the signals before and after filtering, analyze the change of the signal, replay the speech signal, and compare with the original speech signal)