Acoustic imaging of underwater embedded objects: signal simulation for three-dimensional sonar instrumentation

This paper presents a method able to emulate the signals received by a sonar system exploring a submerged environment. The simulation of the response of an underwater scene insonified by a wideband pulse has been based on the reproduction of the interactions of the acoustic field with a buried object, with the seabed surface, and with the sediment volume. The signals gathered by the sonar array are emulated by modeling the surfaces of both the seabed and objects as a dense random grid of small discrete scatterers, by following Rayleigh's law, and by integrating the responses of the scatterers. The roughness effects are simulated by allowing random distances from the actual scatterer positions to their nominal positions on the surface. Sediment-volume inhomogeneities are modeled by a random distribution of the small asymmetrical scattering volumes, characterized by their three-dimensional (3-D) dimensions, densities, and sound velocities. In general, the simulator is very flexible in defining the object, the related scenario, and the major physical parameters involved. A voxel-based beamforming to generate the 3-D images starting with the simulated signals is also presented and briefly discussed. The 3-D images obtained appear very realistic and contain all the expected elements in the right relationships, including the typical speckle noise