ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aPAa6. Atmospheric sound propagation in a turbulent atmosphere over irregular terrain.

Xiao Di

Kenneth E. Gilbert

Appl. Res. Lab. and the Graduate Program in Acoust., Penn State Univ., P.O. Box 30, State College, PA 16804

A phase screen method for atmospheric turbulence and a cascaded conformal mapping technique for irregular terrain are used together to investigate scattering of sound by turbulence into a terrain-generated shadow zone. Comparisons with and without atmospheric turbulence are made for frequencies from 50 to 500 Hz. It is shown that with the near-ground turbulence model of Daigle and a hill similar to that in the Joint Acoustic Propagation Experiment (JAPE), turbulence effects are negligible below approximately 125 Hz. Above 125 Hz, there is considerable scattering into the shadow zone behind the hill. For the data currently available from the JAPE measurements, the theoretical predictions are in good agreement with experiment. [Work supported by the Army Research Laboratory.]