Effect of directivity on the sound field produced by a source above a reflecting plane

Abstract

In this paper, the effect of source directivity on the sound field produced by a source near a reflecting plane by using a collinear array of point sources operating in phase, located above a reflecting plane, but in an otherwise reflection‐free environment is analytically and experimentally investigated. It was found that the presence of the reflecting plane and the source directivity can have a considerable effect on the sound pressure levels (SPL). When radiating a third‐octave band of noise centered at 500 Hz, for example, the variations in SPL with source orientation were as much as 12 dB. Furthermore, the maximum correction factor occurred when the mainlobe of the source directivity pattern pointed toward the reflecting plane rather than, as might be expected, toward the receiver. Finally, reasonably good agreement is found between the measured and corrected SPL, with the rms error being less than 2.6 for the 500‐Hz octave and third‐octave bands.