Abstract:
A mechanism for inobtrusive sub-bottom profiling in adverse ocean floor environments is being developed. Profiling of the ocean bottom has been accomplished using attenuation and relaxation time methods based on dispersion characteristics of chirp sonar pulse reflections developed by Precision Signal, Inc. [LeBlanc et al., J. Acoust. Soc. Am. 91, 116--126 (1992)]. Sediment classification data, using a 20-ms FM chirp sonar pulse in the frequency range of 2--10 kHz, were collected in Narragansett Bay, RI, and compared with core samples [LeBlanc et al., J. Acoust. Soc. Am. 91, 107--115 (1992)]. Results indicate a high correlation between the core-determined sediment properties and the estimates obtained from acoustic measurements to depths of 20 m. This sonar technique is to be implemented using converted torpedo sonar hardware adapted for use by Naval Undersea Warfare Center, Division Newport. The Ocean Bottom Profiler will consist of transmitters, receivers, data storage, and transmission systems of versatile and robust design, which can be adapted for use in towed, ship-mounted, and free-running survey vehicles.