Mode Selection of Wideband Acoustic Signals Using Time-Frequency (Warping) Analysis for Single Hydrophone. Comparison with Array Filtering in Variable Medium

Abstract

broadband air-gun data from SWARM’95 experiment in shallow water area of Atlantic shelf are used to analyze mode filtering using time-frequency analysis in the form of Warping Transform. Sound fluctuations in the presence of nonlinear internal waves are considered using this analysis. Results are compared with mode filtering using vertical line array (VLA). It is shown that Warping Transform allows us to provide mode filtering in shallow water environment, changing in time and space in the presence of moving nonlinear internal waves by single hydrophone only. Temporal variations of mode composition in given case have properties specific for manifestation of horizontal refraction in the form of focusing/defocusing in horizontal plane.