Broadband source signature extraction using a vertical array

Abstract

Source signatures have been extracted from acoustic data received on a large vertical array. Multichannel deconvolution methods were used in conjunction with broadband coherent and incoherent matched-field processors for source signature reconstruction. The signatures were generated by broadband (25–110 Hz) sources located near the first and second convergence zones, approximately 48 and 97 km from the array. Cross-correlation coefficients between known source signatures and deconvolved estimates indicate that faithful reconstructions of both magnitude and phase can be obtained. Use of incoherent noise components from the main diagonals of cross-spectral density matrices produced correlation coefficients ranging from 0.77 to 0.93. Degradation primarily appeared as increased noise in the reconstructed signature. Attempts to include the full spatial coherence of the ambient noise by using off-diagonal matrix components, resulted in correlation coefficients approximately 10% lower. This effect is caused by nonstationarities in the noise field which preclude using an ergodic hypothesis to obtain statistically reliable temporal averages for the cross-spectral density matrices.