Computing acoustic transmission loss using 3D Gaussian ray bundles in geodetic coordinates

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This paper defines a new three-dimensional (3D) Gaussian ray bundling model in geodetic coordinates: latitude, longitude, and altitude. Derivations are provided for 3D refraction, 3D interface reflection, 3D eigenray detection, and a 3D variant of the Comprehensive Acoustic System Simulation (CASS)/Gaussian Ray Bundling (GRAB) model. This approach allows environmental parameters and their derivatives are computed directly in latitude, longitude, and depth directions without reducing the problem to a series of N ×2D Cartesian projections. Our model supports 3D effects such as great circle routes and horizontal refraction in sloped environments. Key test results are included for ray path refraction accuracy using a Munk profile, Gaussian beam projection into the shadow zone for an n2 linear profile, and horizontal refraction from a 3D analytic wedge. Testing to date indicates that this approach has accuracy at least as good as CASS/GRAB, but with improved execution speed benefits for large numbers of targets, and 3D transmission loss effects.

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Journal of Computational Acoustics