生成2KHz和8KHz的混合信号，使该信号通过上述滤波器，观察滤波前后的波形变化和频谱分布情况。

在改信号中加入高斯白噪声，观察滤波前后的波形变化和频谱分布情况。-2KHz and 8KHz generation mixed-signal, so that the signal through the above-mentioned filter, filter before and after observation of the waveform and spectrum distribution of the changes. Add to the signal in white Gaussian noise was observed before and after filtering the waveform and spectrum distribution of the changes.