Analysis of in Situ Acoustical Performance of Concrete Noise Barriers

The need to enhance the people's mobility has produced a significant increase in the environmental pollution, including transportation noise. In order to reduce transportation noise it is possible to act directly on transport media or on the urban environment, by protecting sensitive receptors with techniques for noise reduction. The noise barriers are one of the most common examples of noise reduction devices. In this paper the authors show and discuss the results of an in situ analysis of the acoustical performance of concrete noise barriers, installed in an important highway infrastructure of the Central Italy. The structure of examined barriers is composed of 8 overlapping panels made by autoclaved aerated concrete. The faces of the panels, facing the noise source, can be smooth or machined with high pressure water jets (rough surface with irregular horizontal chamfering) to increase the sound absorption properties. In order to increase the sound absorption of the barriers, till to the higher quality class (A4) indicated in EN 1793-5, semi-cylindrical acoustical absorbers have been designed. They are made by metallic micro-holed envelope with the cavity partially filled by suitably shaped polyester fiber and they can be installed at variable distances from the face of the panel.