Broadband Acoustic Clutter

Abstract

LONG TERM GOALSThe long term goal is to improve performance of low-mid frequency active sonar systems against clutter. OBJECTIVESThe objectives are to identify/understand the mechanisms that lead to clutter and develop models that predict the temporal/spatial/frequency dependence of the observed clutter and background diffuse reverberation. APPROACHThe experimental approach is based upon exploiting both long-range observations of clutter and shortrange, or direct-path observations (seabed scattering and reflection) of the features that give rise to the clutter. Direct path observations offer two significant advantages: a) the uncertainties associated with propagation (through a generally sparsely sampled ocean) are minimized, and b) the measurement geometries are favorable to producing data from which hypotheses about the scattering mechanisms can be directly tested. The theoretical approach for diffuse reverberation was taken and advanced from energy flux methods. This project is part of the Broadband Clutter Initiative Joint Research Project (JRP) including ARL-PSU (USA), DRDC-A (CAN), the NATO Undersea Research Centre (Italy) and NRL-DC (USA). WORK COMPLETEDA short summary of FY09 efforts include: 1) Developed simplfied approach to propagation and reverberation from range-dependent sediment layers (in the adiabatic approximation). Initially tackled range-dependence in layer thickness, though the approach is extensible to range-dependence in all the geoacoustic properties.2) Planned and executed long-range and short-range reverberation, scattering, propagation and reflection experiments for the Clutter09 experiment, April 29 -May 31, 2009. A key platform 1 Report Documentation PageForm Approved OMB No. 0704-0188Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.