Paul A. Baxley
Ocean and Atmospheric Sciences Div., Acoust. Branch, NCCOSC RDTE Div. Code 541, 53560 Hull St., San Diego, CA 92152-5001
The detection of a moving source at low signal-to-noise ratio can be enhanced by taking advantage of the time evolution of matched-field ambiguity surfaces. By including a track search in the matched-field process, track-before-detect (TBD) techniques extract source track information so that the target signal function can be reconstructed, rendering it more detectable. The detection enhancement produced by a shift-then-average (coherently and incoherently) TBD algorithm [Baxley, J. Acoust. Soc. Am. 90, 1844(A) (1993)] is investigated for multitone source-tow data recorded near San Diego during the first and third shallow-water evaluation cell experiment (SWellEX-1 and 3). The 3-knot source-tow traversed a range-independent radial from a FLIP-mounted vertical line array. Previously masked targets were rendered detectable in ambient noise and in the presence of a single loud interferer. Gains in detectability of up to 5 dB above that obtained by straight averaging (no tracking) were obtained for a 6-min averaging time.