Over time, different kinds of defects can appear at noise barriers. For example, this includes holes and slits between screening elements due to accidental destruction and faults during assembly or effects of weather and clogging on absorbing materials. The effect of those defects on the acoustic properties of noise barriers has not been examined in detail yet. The project is meant to close this gap and to provide a catalog which allows to predict the influence of specific defects especially on the sound insulation of the noise barrier and thus on its screening effectivity. Based on the information contained in the catalog, it is possible to take cost efficient action to permanently ensure the protection of immission sites. To compile the catalog, the nationally standardized sound propagation model of the RLS 90 is extended by the description of the sound transmission through the noise barrier together with the geometrical consideration of leakages in the shape of holes and slits. Simulations show the formation of an acoustically critical area behind the leakage in the noise barrier. The boundary of this area can be taken from the catalog for a multitude of geometrically abstracted damages for further comparison to a zoning map. The catalog parameters taken into account are particularly the effective area (product of the transmission coefficient and the area of round leakages) or the effective width (product of the transmission coefficient and the width of leakages in the shape of slits). It is shown that the transmission coefficient of leakages can be predicted reliably by means of the calculation according to MECHEL as well as by measurements at noise barriers in situ. Furthermore, the latter ones are used to successfully validate the models applied to describe the sound transmission coefficient of leakages and the sound propagation behind noise barriers in consideration of the transmission. (Author/publisher)
Samenvatting