Correlation characteristics and travel time differences for hydroacoustic signals under directional reception at different depths

Experimental data are presented for the cross-correlation coefficients and travel time differences of audible signals measured at distances of ～60 and ～120 km in an oceanic waveguide. The signals are received simultaneously by two highly directional vertical arrays (with a main lobe width of ～2°) whose centers are at depths of 200 and 450 m. The radiation depths of the pseudonoise signals were 200 and 400 m. The high correlation coefficients (0.75–0.94) obtained for the signals received at different depths suggest that the changes in the frequency spectra of signals arriving over different paths are almost identical. The small fluctuations of the travel time differences (≤0.43 ms for the “water” signals and ≤0.63 ms for the signals reflected from the sea surface) testify to their high stability.