Vertical Correlation of the Acoustic Field in Deep Water Measured with Explosive Sources

In this paper we report the measurement and analysis on vertical correlations of acoustic signals received by a vertical line array deployed near the sea bottom in deep water. The source data were from one calibration experiment of sound exposure level of explosive charges. The source–receiver range is about 17 km. The sound transmission duct is the well-known reliable acoustic path (RAP). The vertical correlation coefficients are estimated at center frequencies of 300, 600, 1000 and 1500 Hz with 1/3 octave bands. Two types of explosive charges are used with nominal source depths of 50 and 300 m, respectively. The variation of vertical correlation coefficients strongly relies on source depth and center frequency. For each scene, ten groups of experiment data exhibit uniform variation of vertical correlation coefficients with fractional differences due to the fluctuation of ocean waveguide. Besides, the noise-free numerical modeling results reach good agreements with the measured ones, which reflect the stability of RAP as a sound transmission duct in the space/frequency domain. Due to the obvious arrival structures of rays, the theoretical solution of vertical correlation coefficient is derived based on the ray theory. At last, the effects of source–receiver geometry on the variability of vertical correlation are discussed.