Estimation of Array Tilt Using Snapping Shrimp Noise

Snapping shrimp is the dominant source of high-frequency (> 2 kHz) ambient noise in temperate and tropical coastal waters. Since it is abundant, impulsive, and strong, snapping shrimp noise can be useful for passive remote sensing. During a recent experiment conducted in about 100-m deep shallow water, a large number of snapping shrimp sounds were recorded by a large-aperture vertical array (56 m) that was bottom-moored. Localization of the snapping shrimp in range and depth is based on spherical-wave beamforming. Assuming a vertical array without tilt, the localized snaps are confined to a range-depth region bounded by two straight lines with opposite slopes. It is found that the absolute slope corresponds to the array tilt, suggesting that snapping shrimp can serve as a natural source to estimate the vertical array tilt.