说明：  实现一个针对《数字信号处理》课程的仿真系统，通过该系统可以演示或验证课程所学的内容。要求程序具有界面，并能实现以下功能： 产生数字信号和读入语音信号，显示时域和频域波形，在信号上叠加噪声（信噪比分别为20dB、10dB和5dB），显示时域和变换域波形，通过滤波器对其降噪，得到输出信号的频域特性和时间序列。
(A simulation system for "digital signal processing" course is implemented. The system can demonstrate or verify the content of the course. It is required that the program has an interface and can realize the following functions: The time domain and frequency domain waveforms are displayed for the generated digital signal and the read in speech signal, and the noise is superimposed on the signal (the signal-to-noise ratio is 20dB, 10dB and 5dB respectively) to display the time-domain and transform domain waveforms. The frequency-domain characteristics and time series of the output signal are obtained by noise reduction through a filter.)