Mitigation of Biologically Induced Active Sonar Reverberation in Littoral Regions Navy SBIR FY2013.1 Sol No.: Navy SBIR FY2013.1 Topic No.: N131-045 Topic Title: Mitigation of Biologically Induced Active Sonar Reverberation in Littoral Regions Proposal No.: N131-045-0418 Firm: Applied Research in Acoustics LLC 1222 4th Street SW Washington, D.C. 20024-2302 Contact: Jason Summers Phone: (202) 629-9716 Web Site: www.ariacoustics.com Abstract: Applied Research in Acoustics LLC will formulate and develop new concepts and algorithms for data-driven clutter-adaptive waveform-synthesis and CFAR normalization processing based on physical models of resonant backscattering from heterogeneous aggregations of swim-bladder-bearing fish that will significantly improve active sonar detection capability in littoral waters by reducing the number of false contacts and decreasing the amount of display clutter. The new signal processing concepts and algorithms developed and evaluated in this work will comprise (1) clutter-adaptive waveform and matched-filter synthesis using a data-driven approach to mitigate reverberation and clutter due to resonant scattering from fish, (2) clutter-adaptive CFAR normalization of the within-beam time series using model-based and data-driven assessment of range-dependent amplitude statistics, and (3) clutter-adaptive cross-beam and image-based normalization using model-based and data-driven assessment of spatial statistics of clutter from fish. The performance and feasibility of these new concepts and algorithms will be evaluated individually and as an integrated processing system with simulated midfrequency active sonar data representative of the AN/SQS-53C operating in a shallow-water environment with various sources of biologically induced clutter, as generated by a validated sonar-simulation model and a validated analytical model of scattering from heterogeneous aggregations of swim-bladder-bearing fish. Benefits: The proposed research and development will provide a significant improvement in the performance and detection capabilities of Navy active sonar in littoral waters by mitigating the effects of biologically induced active sonar reverberation resulting from resonant backscattering from swim-bladder-bearing fish through data-driven clutter-adaptive waveform-synthesis and normalization processing. Phase I efforts will specifically contribute validated new concepts and algorithms for (1) clutter-adaptive waveform and matched-filter synthesis, (2) clutter-adaptive CFAR normalization of the within-beam time series, and (3) clutter-adaptive cross-beam and image-based normalization. After demonstration of feasibility in Phase I using simulated midfrequency active sonar data and analytical models of scattering from heterogeneous aggregations of swim-bladder-bearing fish, Phase I efforts will provide the foundation for Phase II development of a signal-processing software-library prototype of a clutter reduction functional segment for the AN/SQQ-89A(V)15 to be evaluated with archived AN/SQS-53C data. Unlike hardware updates, this signal-processing approach to mitigation of biologically induced clutter due to reverberation from swim-bladder-bearing fish is highly cost-effective as it maximizes performance of existing hardware with minimal investment and can be easily updated to accommodate hardware changes. Moreover, the signal-processing concepts, algorithms, and software library we propose to develop are extensible across a wide range of active-sonar platforms and particularly suitable for midfrequency sonars such as the AN/SQQ-89(V)15 with AN/SQS-53C or AN/SQS-56 hull arrays, the AN/SQQ-90 with dual-frequency hull arrays, and the Littoral Combat Ship Anti-Submarine Warfare Mission Package. Similar gains can also be realized by commercial midfrequency systems used for subbottom profiling, single-beam and multiple-beam (swath) bathymetry, and acoustic seafloor characterization. Return