Acoustic Greens function extraction from vector ambient noise

Considering the vector hydrophone has the eight shaped directivity pattern in vertical direction, which can restrain the interference caused by distant non-stationary noise sources effectively, a method about acoustic time domain Greens function(TDGF) extraction from vector ambient noise cross-correlation function(NCF) is presented. The sound pressure and vertical velocity correlation models were built based on normal mode theory, on this basis, the longitudinal Green's functions extraction process using sound pressure and vertical velocity are given. The numerical simulations and the experimental data analysis indicated that, compared with sound pressure extraction method, the vertical velocity extraction method can effectively eliminate the bright lines and light area interference which exist in front of the direct wave. In addition, for the same length of noise time sequence, sound pressure extraction method can only extract the direct wave path, while vertical velocity extraction method can extract the bottom reflection path which we are more concerned about. The water depth estimated by time lag between direct wave and bottom reflection wave is consistent well with the measured result.