Abstract:

A novel, lightweight shallow-water hydrophone array was deployed and tested alongside a more conventional similar apparatus during the 1996 Adaptive Beach Monitoring Experiment (ABM-96). Controlled J-11 source tows (145-dB tones between 70 and 700 Hz) and local shipping provided a rich assortment of acoustic signals for intercomparison during a 6-h period. The new system, ULITE (ultralightweight sensor system), was deployed alongside the Marine Physical Laboratory's SRP Array in approximately 13-m water depth. The deployment of ULITE was conducted by hand from a 7-m-long vessel in approximately 1 h. The heaviest component of the system is a 5-kg anchor attached to the end of the ULITE array to prevent movement along the seafloor. Broadcast source tones were observed on single phones in the ULITE array. Received signal excess was, typically, 20--30 dB. The transmissions were simultaneously recorded on the nearby (within 100 m) SRP seafloor array. These data sets represent the first opportunity to conduct a quantitative intercomparison (i.e., single-phone and beamformed spectral ratios) between the ULITE array and a time-proven conventional array. Since the individual hydrophones of both systems are calibrated, a meaningful comparison of absolute levels is possible. [Work supported by ONR 321SS.]