几种常用的功率谱估计方法：相关函数法(BT 法)，周期图法( periodogram)，Bartlett 法，Welch 法，AR 功率谱曲线( p=50)(Several commonly used power spectrum estimation methods: correlation function method (BT method), periodogram method, Bartlett method, Welch method, AR power spectrum curve (p = 50))