Abstract:

An intercomparison is presented of multi-tone, low-level signal detectability in a shallow water environment using various array configurations and processing approaches. The data were collected west of Point Loma in 200-m-deep water during SWellEx-96 which was carried out in May 1996. The multi-tone transmissions covered the 50-400 Hz band and consisted of 13 sets of tonals each having a pilot tone and 4 lower-level tonals. These were broadcast from a source towed at 60-m depth. Two 120-m aperture, 64-element arrays were deployed from the R/P FLIP---a vertical array and a tilted vertical array (tilted westerly at 45 deg). In addition, a 240-m aperture, 32-element horizontal array (slightly bowed) was deployed on the seafloor approximately 2-km south of FLIP and oriented SW to NE. Broadband adaptive spatial processing has been carried out on the data; matched-field processing in the case of the two vertical arrays and both matched-field processing and plane-wave beamforming in the case of the horizontal array. The low-level signal detectability results for the various array configurations and processing approaches will be intercompared. [Work supported by ONR, Code 321(US).]