Inferring bottom acoustic properties from AN/SQQ-32 Sonar Reverberation data

Abstract

Inversion techniques are used to infer bottom geoacoustic properties using AN/SQQ-32 Reverberation Level (RL) data gathered by USS Avenger (MCM-1) in Rhode Island Sound in February 1993. Based on the hypothesis that the magnitude of backscattered energy is directly related to the acoustic reflectivity of the seabed, a statistical analysis of beam RL time series was conducted to determine its correlation with sediment geoacoustic character. A technique was developed using the deviation of the RL for an individual ping!beam from an area-wide average RL to generate geographic maps illustrating bottom geoacoustic characteristics. Resulting plots of 'relative reflectivity' not only agreed with the existing descriptions of sediment distribution, but also provided more detailed spatial representation of bottom geoacoustic distribution. This highlighted the gross inadequacies, particularly in spatial resolution, of existing information on bottom geoacoustic distribution. These plots, when produced using appropriately small sample intervals, have sufficient spatial resolution to expose MCM clutter density information. Geographic maps of relative reflectivity can provide an invaluable aid to planning search strategy, a surveying tool to compare clutter densities, appropriate geoacoustic parameters for accurate model (including full wave) predictions, and a means of real time performance monitoring and assessment (providing the ability to revise and modify search strategy)