ABSTRACT
To design noise barriers with optimum acoustic performance, it is important to have accurate methods for predicting their sound reduction. The diffraction of sound by a semi-infinite rigid plane is a classical problem in wave theory, dating back to the nineteenth century. There was renewed interest in the problem between the 1970s and early 1980s in connection with the acoustic effectiveness of outdoor noise barriers. Many approximate analytical solutions for diffraction by a half plane include the physical interpretation of diffraction suggested by Young and Fresnel. The MacDonald solution has been adapted to include the sound fields due to rays diffracted around the two vertical edges of a finite-length barrier. If the calculation demands an accurate estimation on both the amplitude and phase of the diffracted waves, then the MacDonald solution or the Hadden and Pierce solution should be used although the latter solution will give an accurate solution for both source and receiver locating very close to the barrier.
