Seabed loss and dispersion analysis of broadband propagation data measured in deep water basin

Experimental acoustic data taken in a deep-water environment are analyzed for information on the intrinsic attenuation and volume scattering in the seabed. Sound Underwater Signaling (SUS) explosive sources were deployed in the Gulf of Oman basin with a water depth of about 3300 m. Received pressure time series were recorded on three hydrophones located at about 500, 1650, and 3200 m depth. The sound speed profile is downward refracting, and the seabed is a thick mud sediment with a sound speed ratio of less than unity. A positive sound speed depth gradient is the main mechanism that returns energy to the water column. The time series arrival structure for range scales of about 80 km is composed of a well-defined sequence of ray-like arrivals corresponding to an increasing number of bottom interactions with deeper turning points in the sediment. Time-frequency dispersion analyses of modeled and measured received time series in the 5–600 Hz band are applied in identifying the frequency dependence of loss mechanisms in the seabed. [Work supported by ONR.]