Noise radiation by sources near to plane reflecting surfaces

Abstract

The object of this investigation was to gain information and understanding sufficient to enable the sound fields of noise sources close to room boundaries to be described. The effects of nearby reflecting surfaces on the sound power output and directional radiation of noise sources have been studied, and an existing theory for the far field case has been developed to cover near field directional radiation patterns. For a number of simple sources, practical measurements have been in good agreement with theory for the sound power output of the source, the variation of sound pressure level with distance from the source, and the qualitative determination of near field directional radiation patterns. The information obtained from this work is applicable to noise sources in practical environments such as domestic living rooms, where the direct sound field produced by a gas fire installed in a hearth with hard reflecting surfaces is analogous to that produced by an experimental source close to two perpendicular reflecting planes in an otherwise free field.