Beamformer waveguide invariant source localization on the New Jersey shelf (USA) during winter acoustic propagation conditions—RAGS03

Horizontal and vertical beamformer (waveguide) invariants are used to robustly localize broadband noise sources (ships) using signals in the 50–200‐Hz band. The localization is realized by using signatures recorded on one horizontal and three vertical arrays. In brief, waveguide invariant theory applied to beamforming by two vertical arrays provides a range ratio of the source to the receivers. Beamforming by a horizontal array provides time‐evolving spectrum for a particular look direction (LOFARgram). As a result the trajectories of the striations observed in LOFARgrams can be used to estimate the speed, range and direction of a broadband source. In December 2003 the Naval Research Laboratory moored three vertical arrays and one horizontal array at ranges of 10, 20 and 30 km from two fixed acoustic sources on the New Jersey (USA) shelf. Acoustic signatures from passing merchant and research vessels were recorded on the arrays and used to demonstrate source localization. [Work supported by ONR.]