Two schemes for forward scattering detection: An experimental demonstration

Forward scattering always occurs when an intruder moves into an underwater area between a source and a receiver. The detection of this forward-scattered signal is a challenge because a strong direct blast overwhelms the forward-scattered signal. The key for the detection is to suppress the direct blast and extract the aberration from the background acoustic field. Two schemes of the detection are proposed, one with a principal component analysis on the vertical beam output, and another with adaptive cancellation of direct blast on the received signals. Both the schemes are validated in a lake experiment. The results show that the field was up to 10 dB above the background when the intruder is crossing, compared with 3 dB maximum around the direct blast with direct matched filtering.