Sound Exposure Level Prediction for Impulse Sound Sources Above Variable Terrain

Abstract : The influence of the ground surface makes it difficult to calculate the propagation of impulse noise from Army type blasts such as that produced by heavy-weapons fire on training ranges. This study developed the computer program gtdcom, which extends the Geometrical Theory of Diffraction (GTD) propagation model to include realistic, three-dimensional terrain, broadband sounds (blast waves), and frequency weighting factors. This report describes the theoretical basis used to broaden the GTD model, and briefly outlines the use of GTDCOM. The new program was interfaced with the Geographic Resources Analysis Support System (GRASS) to calculate sound exposure levels (SELs) from blast sources using map elevation contour data. A user specifies the source position of the blast, a charge size, and an expected frequency weighting factor; the program calculates the SEL for each terrain cell, displays the results on the screen, and prepares a contour map for printer output.... GTDCOM, Blast noise, Geometrical theory of diffraction propogation model.