Noise attenuation by finite barriers.

The work described in this thesis deals with the noise reduction performance of plane acoustic barriers of finite dimensions. Equations are developed for prediction of sound attenuation based on Fresnel-Kirchhoff diffraction theory. The main feature of this technique is that attenuation can be predicted regardless of the shape and size of the barrier and of the proximity of source and receiver to the barrier. The theory is initially developed for the case of free-field environments and is subsequently extended to reflecting ground conditions. Computer programs were developed to perform the attenuation calculations in given environments. The programs are driven by a set of parameters which uniquely define the source, barrier and environmental configuration. Experimental work was carried out in an anechoic chamber using a series of different source and barrier configurations. The experimental results were tested against the theory by applying the appropriate parameter values to the computer programs.