Using CEN/TS 1793-4 to develop an acoustically effective added device for road traffic noise barriers (invited lecture)

Part of the market of road traffic noise reducing devices is constituted of products to be added on the top of noise reducing devices and intended to contribute to sound attenuation acting primarily on the diffracted sound field (“added devices”), but as a matter of fact few of these devices are distributed on the European market with a certified performance. The intrinsic characteristics of sound diffraction of added devices can be assessed according to the European technical specification CEN/TS 1793-4, which became available at the end of 2003. The paper reports the application of this European test method to select and optimize a new industrial product, now protected by a patent. A test site was set up to carry out the research. Then full scale measurements were done on prototypal added devices with different shapes, with and without a sound absorbing treatment. The experimental results, here summarised, permitted the selection of the best shape/absorption combination, which was further refined to get the final product, which is not only acoustically effective but also cost effective.