中文说明： 读入二维信号，加入高斯噪声，对其进行3层小波分解，并用小波硬，软阈值进行去噪。显示原始信号，第2,3尺度上的低频，以及硬，软阈值去噪后的图像。
English Description：
The two-dimensional signal is read in, Gaussian noise is added, three-level wavelet decomposition is carried out, and wavelet hard and soft threshold is used for denoising. Display the original signal, the low frequency on the second and third scales, and the image after hard and soft threshold denoising.