Effect of oceanography on broadband acoustic wave propagation in a range dependent shallow water environment

To investigate the effects of oceanographic variability on broadband acoustic wave propagation in shallow water environments, two experiments were carried out on the New England continental shelf region in 2017 and 2022, respectively. Towed sources were used to transmit chirp waveforms over the frequency ranges of 0.5—1.25 kHz and 1.5 – 4.0 kHz on the same acoustic tracks. The broadband acoustic transmissions were received by vertical acoustic arrays with multiple hydrophones. In 2017, the sound speed in the water column was isovelocity while in 2022 the presence of a duct at the depth of 20 m and upward refracting conditions reduced the interaction of acoustic transmissions with the seafloor compared to the experiment in 2017. Experimental observations show the importance of the water column on bottom interacting broadband waveforms causing challenges for the inversion algorithms. In this paper, we present acoustic and oceanographic results showing how the variability of sound speed could change the characteristics of the broadband transmission. Modeled results versus experimental data are discussed. [Work supported by ONR.]