Calculation of a source spectrum using matched-field tracking

An underwater acoustic source can be detected by finding the best match between a measured set of covariance matrix elements and those calculated for possible tracks [H. Bucker, ‘‘Matched-field tracking in shallow water,’’ J. Acoust. Soc. Am. (to be published)]. Let (glft) be the measured elements and (ĝlft) be the elements calculated for the best track of a unit source. Here, index l refers to a pair of sensors, f to a frequency bin, and t is for different times. Then a plot of S(f,t)=∑lglft/∑lĝlft is a Lofargram in which the effects of the multipath propagation have, at least in part, been removed. Of course, the success of the deconvolution depends upon the accuracy of the propagation model and contamination of other sound sources. Several examples will be presented to illustrate the method.