An underwater acoustic detection experiment based on forward scattering in a time reversal mirror

Abstract

Following earlier work by Song et al. [IEEE, J. Ocean. Eng. 28, (2003)] we conducted an underwater acoustic barrier experiment based upon forward scattering in a time reversal mirror. The experiment was conducted at a carrier frequency of 15 kHz in a shallow water waveguide. The waveguide length was about 16 water depths with one interface being an undulating, soft seafloor. After establishing a focus at one end of the waveguide, stationary and moving objects were placed in the water column, including an autonomous undersea vehicle (AUV). Before and after comparison of the received acoustic signal, including the temporal and spatial abberation of the focus, provided object detection. Several anomaly detection techniques were applied to the acoustic data in post-processing. Target speed was observed to be a discriminator in anomaly detection performance, suggesting that a combination of different anomaly detection techniques is probably desirable in addressing the moving target problem. [Work supported by NATO and ONR.]