Building a bottom scatter database from measured bottom scatter data in the eastern Mediterranean Sea

Abstract

The current U.S. Navy Standard bottom scatter database for low frequencies (up to 5 kHz) is Lambert’s Law with a mu coefficient of −27 dB for the world. In recent years, work to characterize scattering from both rough interfaces and the sub-bottom volume has greatly increased the understanding of acoustic interaction with the ocean bottom. However, the analysis of measured bottom scatter data requires an approach that includes the effects of the measurement geometry, higher-order multipaths, and contributions from the water-sediment interface, sub-bottom volume, and the sediment–basement interface. The SCARAB (scattering and reverberation from the bottom) model along with an automated inversion approach (simulated annealing with a downhill simplex) is designed to invert measured bottom scatter data for seven bottom scatter parameters. These seven parameters characterize the water–sediment interface, sub-bottom volume, and sediment–basement interface using a spectral representation for each. The SCARAB model is being used to analyze bottom scatter data measured by navoceano in the Eastern Mediterranean Sea and produce a database for prediction of bottom scattering strength for active sonar systems. The database is to be submitted to the OAML-SRB in late 1999. [This work is being sponsored by SPAWAR (PMW-185) under ONR management.]