Diffraction by absorbent wide barriers

Abstract

Wide barriers of a trapezoidal shape are investigated analytically and experimentally. The analytic model for the diffracted pressure is basedon the geometrical theory of diffraction. The incident ray is considered to undergo double diffraction, once at each of the edges of the two back‐to‐back wedges of the trapezoidal barrier. Thus, the second ray from first wedge to the second must graze the upper surface of the wide barrier. For the double diffraction calculations, the analytic solution for the diffraction by an absorbent single wedge, as originally developed by Malyuzhinets, is used. However, his solution breaks down on the surfaces of absorbent wedges. A correction solution was thus developed for rays that graze the surface of an absorbent wedge, facilitating a model for an absorbent wide barrier. Experiments on ⅕ scale models of hard and absorbent wide barriers were also conducted inside a gymnasium, where harmonic point sources as well as incoherent A‐weighted line noise sources were used. The prediction of the analytic models and the experimental data compare favorably for point to point propagation. [Work supported by National Cooperative Highway Research Program—National Research Council.]