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A generalized polar coordinate method for sound propagation over large-scale irregular terrain.

The polar coordinate method in You [Ph.D. thesis, The University of Mississippi (1993)] is rederived in differential form and is generalized by defining a local, continuously varying, radius of curvature. The generalization makes it possible to compute sound propagation over arbitrary large-scale terrain where the local radii of curvature are much larger than an acoustic wavelength. For a simple hill, both the original and generalized method are in good agreement with measured low-frequency propagation loss data. The generalized method is applied to more complex terrain in a numerical example. The example demonstrates the utility of the method and also shows that complex terrain can have a significant effect on low-frequency sound propagation, even when the slope angles are small.