Moving source 2D-hologram in the presence of intensive internal waves in SWARM-95 experiment

This paper presents the holographic signal processing results from an acoustical oceanography experiment on the New Jersey continental shelf called SWARM-95. This experiment that was conducted in summer of 1995 aimed at propagation of broadband acoustic signals in the presence of intensive internal waves (IIW). Impulsive acoustic signals were from a moving source. The IIW caused modes coupling and significant 3D acoustic effects (Badiey M. et al., JASA, 117(2): 613–625). The current research is based on holographic signal processing (Pereselkov S., Kuz’kin V., JASA, 151(2): 666- 676) utilizing holographic signal processing. Here, the sound intensity distributions in frequency-time coordinates, called the source interferogram, is analyzed using a 2D Fourier transform (2D-FT). The result of the 2D-FT is called the Fourier-hologram (hologram). Two distinct sets of spectral spots were identified in the hologram of the moving source. The first set corresponds to the sound field in an unperturbed waveguide (without IIW). The second set relates to the hydrodynamic perturbation of the sound field caused by IIW. Such a hologram structure allows for the reconstruction of the parameters of the moving source. Results of this research can be used for detection and localization of Autonomous Underwater Vehicles (AUV). [This research was supported by a grant from the Russian Science Foundation (grant number 23-61-10024).]