Analysis of experiments on diffraction of sound by rigid screens

Abstract

Measurements made in an anechoic chamber at NASA Langley Research Center of the sound from a point source diffracted around a rigid screen are presented. Two cases of interest are discussed, the first concerns sound propagating in still air, the second involves low-Mach-number ambient flow past the screen with the trailing edge as the diffracting edge. The results of these measurements are compared with calculations based on (i) an analysis of diffraction by rigid screens by one of the authors, (ii) an extension of Candel's theory of plane wave diffraction in a moving medium to the point source case, and (iii) a recently developed numerical technique for obtaining the diffracted pressure field when the source and receiver are not necessarily far from the diffracting surface.