Effectiveness of screens application depending on an urban structure arrangement

摘要

Diffraction is this phenomenon, which accounts for the screen efficiency, thus the source position in relation to the diffracting wedge and emitted noise spectrum are the decisive factors. In an urban area when a screen is applied as a protector against traffic noise, it is also an additional reflecting plane. The simulation program PROP7 allows to observe the differences in the equivalent sound level resulting from single and double screens application in different building arrangements. In the PROP7 program, buildings are modeled as shoeboxes while plane screens are represented by panels of limited dimensions. Wave interactions during propagation process include reflections from the ground and building walls up to an arbitrary order, and single and double diffraction at wedges. The acoustical energy emitted by a road as a noise source is related to the sound exposure level of an individual vehicles pass-by. The road geometry considers a number of lanes and their positions. A vehicle movement is replaced by a set of its discrete positions along the route. Thus, when vehicles are divided into classes, for each class the equivalent point source of a given height above ground and power spectrum is assumed. A vehicle stream on a lane is characterized by a number of classes and, for each class, by an average speed and flow rate.