说明：  对产生30组N点均值为零，方差为1的平稳高斯白噪声，分别计算N=64，128，256，512时的功率谱估计值
(For generating 30 groups of stationary Gaussian white noise with the mean value of n points being zero and the variance of 1, the power spectrum estimation figures with n = 64128256512 are calculated respectively)