Time delay estimation of broadband acoustic signals and its defense applications

The measurement of the difference in the times of arrival (or time delay) of an acoustic signal at two spatially separated sensors is fundamental to localizing its source. For continuous broadband signals, the time delay is best estimated by the generalized cross-correlation of a pair of sensor outputs. The lag at which the generalized cross-correlation function reaches its maximum value provides an estimate of the time delay. Generalized cross-correlograms are presented for sensor output data recorded at sea on a submarine. The correct peak is readily identified by cross-correlating the conventional (and also the adaptive) beamformer outputs of a pair of widely-spaced arrays, rather than the outputs of two single hydrophones with the same separation distance (66.3 m). Similarly, the use of various prefiltering methods is shown to suppress secondary (ambiguous) peaks in the cross-correlogram. This approach is then extended to include mechanical and biological underwater acoustic transient signals with the...