Vertical Correlation and Array Gain Analysis for Vertical Line Array in Deep Water

Abstract

<jats:p>Array gain (AG) is significant in evaluating the detection performance of the vertical line array, which is directly determined by the correlation of signal and noise, respectively. In this paper, we analyze the vertical correlation for a 16-element vertical line array experimented in the deep ocean in 2016. The ray interference theory is utilized to interpret the mechanism of the vertical correlation of the sound field in different zones. In the direct-arrival zone, the direct rays and once-surface-reflected rays are two dominated components, whose arrival time difference for each element are nearly the same, and the vertical correlation is high. In the shadow zone, the sound field is mainly dominated by bottom-reflected rays and the vertical correlation decreases due to different grazing angles and arrival times of each ray. Different from the previous assumption of noise independence, the effect of noise correlation on the AG is analyzed through the measured marine environmental noise. Results indicate that the noise correlation coefficients in two zones are low but not 0. In the direct-arrival zone, AG is about 10 dB, very close to the ideal value of 10 log M . AG even exceeds it when NG is negative. Moreover, AG in the direct-arrival zone is higher than the one in the shadow zone.</jats:p>

Effects of Climate Change on Oceanic Sonar Use in the Upper European Continental Shelf

“…Here, SN R is the Signal-to-Noise Ratio, SL is the source level, T Lc = 10 log 10 ( d d ref ) is the transmission loss due to the cylindrical spread of sound where d d ref is the ratio of the initial reference distance * to the distance over which the sound travels 3 , T La is the transmission loss due to attenuation, T S is the target strength, and N L is the noise level. More advanced navigational systems will use beamforming 4 to only listen for signals from a specific direction by using a spatial array of multiple receivers, effectively reducing the noise level and adding an additional term +AG for array gain 5 .…”