Source level estimation of snapping shrimp sounds in shallow water environment

Snapping shrimp noise, with high source level and broadband spectrum, can disrupt the operation of sonar and underwater acoustic communication systems. To solve the multi-path and multi-source problem in estimating in situ source level of snapping shrimp noise, a method of automatically estimating source level of snapping shrimp noise is developed. A large-aperture vertical line array is used to locate individual snaps in the near field based on matched-filed processing. As the snaps are strong and transient, the threshold detection method is used to obtain the arrival time of the snapping shrimp signals, then the amplitude is normalized to solve the multi-source problem with large dynamic range. Arrival time structure of the direct path is calculated using ray theory as replicas to match with the data using spherical-wave beamforming. The source level is then calculated using the localization results and the original snapping shrimp sounds. The average peak-to-peak source level of snapping shrimp noise measured in East China Sea is 173 dB re: 1 µPa @ 1 m, with an interquartile range of 168∼175 dB re: 1 µPa @ 1 m.