Hydrophone self-localisation using travel times estimated from ocean noise cross-correlations

Abstract

Approximation of acoustic Green’s functions through cross-correlation of acoustic signals in the ocean is a relatively young field that has become an area of interest over the past few years. Although the amplitudes of these estimates generally differ from those of the true Green’s Function, the estimated arrival structure can be highly accurate. Interhydrophone travel times extracted from these Green’s Function estimates can therefore be relied upon for practical applications. Acoustic data were collected for two weeks during late 2006 on an L-shaped array (combination of vertical hydrophone line array and horizontal bottom-mounted hydrophone line array) that was deployed in shallow water ( 70- 75m depth) on the New Jersey Shelf. The data were cross-correlated and acoustic Green’s Functions were subsequently estimated. This paper describes how the inter-hydrophone travel times extracted from these Green’s Function estimates were used to self-localise the array. Successful implementation of this cross-correlation derived travel-time application provided the array geometry information necessary for both ambient and active source acoustic data recorded on the array to be useful for other analyses.