Three-dimensional noise modeling in a submarine canyon

The ambient sound field due to wind generate surface noise in an idealized Gaussian submarine canyon can be described using the method of normal mode decomposition applied to a three-dimensional longitudinally invariant wave-guide. The modal decomposition is carried out in the vertical and across-canyon horizontal directions and gives a semi-analytical solution describing the three-dimensional topographic effects on the spatial distribution of the noise, the power spectrum, and the vertical and horizontal coherences. Additionally, the noise field can be computed using wave-equation reciprocity and either a three-dimensional cylindrical co-ordinates parabolic equation (PE) or an Nx2D PE sound propagation model. Inter-comparison of these models highlights the effect of the three-dimensional topography on the vertical coherence and mean-noise level as a function of arrival direction relative to the canyon’s axis. These effects include the focusing of noise along the canyon axis and the frequency perturbation of vertical coherence minima.