ASA 126th Meeting Denver 1993 October 4-8

5aPA6. Comparisons of experimental measurements of sound propagation over a hill and the polar parabolic equation method.

Chulsso You Henry E. Bass

Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677

Kenneth E. Gilbert

Penn State Univ., State College, PA 16804

The polar parabolic equation (POPE) method, which introduces the boundary fitting coordinates into the parabolic equation (PE) method, was developed to solve for sound propagation over a curved surface and over irregular terrain (hills) [X. Di et al., J. Acoust. Soc. Am. 92, 2431 (A) (1992)]. POPE can include realistic sound-speed profiles and ground impedance. Predictions based upon the POPE have been compared to measurements at the JAPE 91 (Joint Acoustic Propagation Experiment) terrain masking experiment at White Sands Missile Range, New Mexico during the period 27--28 July 1991. The sound sources were hovering helicopters at the base of a hill and far away from the hill. In the JAPE data, the relative sound pressure level decreases rapidly from the top of the hill and becomes nearly constant along the base of the hill. This characteristic feature is well predicted by the polar parabolic equation calculations. POPE method appears to be an accurate means for predicting sound propagation over realistic terrain.