Noise reduction by barriers

A literature review has been prepared to summarize the present state of knowledge concerning the attenuation by barriers. Frequently used prediction methods for the performance of screen-type barriers are analyzed with respect to errors resulting from particular source and receiver positions, from ground reflections, from absorptive properties of the barrier and the ground, and from the influence of wind. Recently developed formulas describing the diffraction by wedge-shaped and wide barriers are reduced to simplified methods for the prediction of the shielding achievable in comparison to screen-type barriers. Unsolved problems apparent from discrepancies of the field performance of barriers and the results of theoretical and model studies are summarized to outline areas requiring further research.