ASA 124th Meeting New Orleans 1992 October

4aPA8. A nonreflecting boundary condition for use in PE calculations of sound propagation in air.

M. E. Mayfield

Dept. of Math. and Comput. Sci., Hood College, Frederick, MD 21701-8575

D. J. Thomson

Defence Res. Estab. Pacific, FMO Victoria, BC V0S 1B0, Canada

Although the parabolic equation (PE) method has long been used to model underwater sound propagation, its applicability to outdoor sound propagation has been realized only recently [e.g., K. E. Gilbert and M. J. White, J. Acoust. Soc. Am. 85, 630--637 (1989)]. In ocean acoustics, an absorbing layer is usually appended to the base of the computational grid to suppress unwanted reflections that arise from a Dirichlet boundary condition imposed at a finite distance below the ocean-bottom interface. For sound propagation in air, however, this local boundary condition must be applied at the top (z=H) of an absorbing layer that occupies the region h