(2). 采用汉明窗，分段长度L=32，用修正的周期图法进行谱估计，并分析数据长度N，分段长度M对谱估计结果的影响。-(2) using Hamming window, segment length L = 32, the modified periodogram method of spectral estimation and analysis of data length N, the length M of the sub-spectrum estimation results.