Application of the Beilis-Tappert parabolic equation method to sound propagation over irregular terrain

作者：Parakkal Santosh; Gilbert Kenneth E^*; Di Xiao

来源：Journal of the Acoustical Society of America, 2012, 131(2): 1039-1046.

DOI：10.1121/1.3676693

The Beilis-Tappert (1979) parabolic equation method is attractive for irregular terrain because it treats surface variations in terms of a simple multiplicative factor (%26quot;phase screen%26quot;). However, implementing the exact sloping-surface impedance condition is problematic if one wants the computational efficiency of a Fourier parabolic equation algorithm. This article investigates an approximate flat-ground impedance condition that allows the Beilis-Tappert phase screen method to be used with a Fourier algorithm without any added complications. The exact sloping-surface impedance condition is derived and applied to propagation predictions over hills with maximum slopes from 5 degrees to 22 degrees. The predictions with the exact impedance condition are compared to predictions using the approximate flat-ground impedance condition. It is found that for slopes less than 15 degrees-20 degrees, the flat-ground impedance condition is sufficiently accurate. For slopes greater than approximately 20 degrees, the limiting factor on numerical accuracy is not the flat-ground impedance approximation, but rather the narrow-angle approximation required by the Beilis-Tappert method. Thus, within the 20 degrees limitation and using the flat-ground impedance condition with a Fourier parabolic equation, sound propagation over irregular terrain can be computed simply, efficiently, and accurately.

• 出版日期2012-2