Brian G. Ferguson
Maritime Operations Div., Defence Sci. and Technol. Org., P. O. Box 44, Pyrmont 2009, Australia
Information on the various sound sources that contribute energy to the underwater acoustic environment is often obtained by processing the data from a thin flexible line array of hydrophones towed behind a vessel. The acoustic data from the array are processed digitally in the frequency and spatial domains. The process of spatial filtering, which is commonly referred to as beamforming, assumes that the horizontal line array is straight with the transverse displacements of the hydrophones being zero with respect to the array axis. Using real acoustic data, this paper shows the effects on conventional and adaptive beamformers when these transverse displacements are finite and the array shape is nonlinear. Furthermore, signal processing techniques are presented that significantly reduce the influence of these effects on the performance of the beamformers. By processing the array's acoustic data when a plane-wave acoustic source is present, these techniques estimate the horizontal and transverse displacements of the hydrophones for subsequent input to the spatial filters.