A Nondimensional Parameterization for Sound Propagation in the Atmosphere

Report No. ARL-TR-2950
Authors: Michael Mungiole and D. Keith Wilson
Date/Pages: March 2003; 22 pages
Abstract: Parabolic equation (PE) techniques have been successfully used to obtain numerical solutions of sound pressure attenuation in which sound propagation is affected by turbulence and vertical gradients in wind and temperature. The PE models generally produce accurate attenuation values, but the execution time is excessive for applications when near real-time results are required. To obtain sound level attenuation predictions at selected locations more quickly, we are developing an artificial neural network. As a first step in this effort, the PE and boundary conditions were modified to obtain a nondimensional version, written in the MATLAB code. This nondimensional version was developed to be used to train the artificial neural network because a fewer number of parameters (seven) would be required to be specified, resulting in a reduced number of model runs to develop the training algorithm. This report documents the derivation of the appropriate equations that are used in the modified (nondimensional) version of the acoustic propagation model. In addition, graphical data are provided that identify the sensitivity of sound pressure attenuation to each of the seven nondimensional parameters.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 2003