通过给出的随机过程，该随机过程是由3个实正弦信号组成，归一化频率分别为0.1,0.25,0.27，其中相位是相互独立在【0,2*pi】上分布的随机相位；噪声是均值为0、方差为1的实高斯白噪声，信噪比为30db,30db,27db,观测样本数为N，通过bartlett法，Welch法，周期图法计算随机过程的概率谱-Given by stochastic process, the stochastic process is composed of three real sine signal, the normalized frequency were 0.1, 0.25, 0.27, including phase is independent in [0, 2* PI] on the distribution of random phase　Noise variance is the mean to 0, 1 real gaussian white noise, signal to noise ratio of 30 db, 30 db, db, and the observation sample for N, by bartlett, Welch, periodogram spectrum method to calculate the probability of the random process