采用子带二值加权累积的经验格林函数提取

Empirical Green’s function extraction based on binary sub-band weighted stacking

提出一种采用子带二值加权累积的海洋环境噪声互相关函数(NCF)提取经验格林函数(EGF)方法。首先将每一快拍NCF在频域划分为多个子带,每个子带内根据“累积后提取的EGF信噪比增加”的准则,确定各快拍NCF的加权系数为0或1,将各子带的加权累积结果谱白化后在频域拼接,再反傅里叶变换得到时域EGF。子带二值加权累积方法实现了每一快拍NCF累积前的频率自动选择,相比于已有的原始累积方法与时域二值加权累积算法,可以有效提高从较宽频率带宽的海洋环境噪声中提取EGF的信噪比。海试实验数据验证了该方法的有效性与优越性。

A method to extract empirical Green’s function(EGF)from oceanic ambient noise cross-correlation function(NCF)based on sub-band binary weighted stacking is proposed.Firstly,each snapshot of NCF is divided into multiple sub-bands in the frequency domain.In each sub-band,the weighting coefficient of each snapshot NCF is determined to be 0 or 1 according to an increase in the signal-to-noise ratio of extracted EGF after stacking.The stacked sub-band results are spectral whitened and spliced in the frequency domain,and then the inverse Fourier transform is used to obtain the time domain EGF.The sub-band binary weighted stacking method realizes the adaptive selection of the frequency of each snapshot of NCF before stacking.Compared with the original stacking method and the time-domain binary stacking algorithm,the proposed method can effectively improve the signal-to-noise ratio of EGF extracted from oceanic ambient noise with a relatively wide frequency bandwidth.The sea trial data verifies the effectiveness and superiority of the proposed method.