High-Frequency Sound Interaction with Ocean Sediments and with Objects in the Vicinity of the Water/Sediment Interface and Mid-Frequency Shallow Water Propagation and Scattering.

摘要

Development of accurate models for acoustic scattering from, penetration into, and propagation within shallow water ocean sediments. Development of reliable methods for modeling acoustic detection of buried objects at subcritical grazing angles. Improving our understanding and modeling of shallow water propagation. Our work will contribute to the objectives of improving the Navy's ability to detect and classify buried mines in shallow water and of improving sonar performance in shallow water in general. Relative to the first two long-term goals our specific objective for FY07 was to document both the results from the Sediment Acoustics Experiment in 2004 (SAX04) and the associated analysis and modeling techniques that were developed. Those results include (1) measurement of backscattering levels from buried objects at subcritical grazing angles using synthetic aperture sonar (SAS) measurements in order to test buried-object-detection modeling accuracy; (2) identification of the dominant high-frequency backscattering and subcritical penetration mechanisms, including a demonstration that these acoustic processes can be quantitatively modeled based on measured sediment properties; and (3) measurement of sediment attenuation and sound speed over a wide range of frequencies and the use these results, combined with measured sediment properties, to test the validity of sediment acoustic models, and in particular the poroelastic (Biot) model. Addressing these as well as several ancillary issues has led to the preparation of 9 articles for submission to a Special Issue of the IEEE Journal of Oceanic Engineering on Sediments Acoustic Processes scheduled for publication in 2008.