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Abstract

Ocean sounds play a major role in disturbances to the underwater transmission of acoustic signals. Because of the waveguide nature of shallow water, noise characteristics are highly variable. Similarly, because of the reflection of noise from the bottom surface and biological activities, the speed of sound varies substantially. Noise field characterisation is complex in shallow water regions. Ambient noise coherence analyses in shallow waters provide information about channel characteristics that could be helpful for underwater acoustic signal transmission. Ambient noise data were collected in the Bay of Bengal by considering factors including hydrophone depth, wind speed, noise type, sea depth, engine state, wind speed, temperature, biological noise, nonbiological noise, and wind direction. Finally, power spectral densities were plotted under various conditions for the collected noise data. For similar noise patterns, the observed variation in coherence was very low. A high variation in coherence was exhibited in data containing noise that arose from varying sources.

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