A combination of a road restraint system and a noise reducing device

Abstract

Based on measurements performed on a low-height noise barrier, an investigation was commenced on where such product could be implemented with respect to both noise reduction and to road restraint requirements, including traffic safety. By using three noise prediction tools, SoundPLAN (version 7.4), a Boundary Element Method (BEM) and an analytic solution, the screen insertion losses could be estimated and compared. The screen heights that were studied were 1.2m and 1.4m. The noise reducing effects of these screens were investigated in two real cases that were given by Malmö Stad and in a theoretical case. Standards for both a road restraint system and a noise reducing devise have been studied and summarised to facilitate the development of the combined system. The insertion losses for the two heights were 10 dB(A) and 11 dB(A) respectively when calculating for the theoretical situation. For the real case scenarios, the insertion losses were deteriorated to around 3 dB(A), concluded to be due to reflections in surrounding facades. The deviations in insertion loss between the different calculation methods was at most 2 dB but the results for the increased barrier height showed that a higher insertion loss could be achieved. The use of the BEM results, which were pre-calculated and provided to the project, showed that an absorbing screen should be considered when it comes to a lowheight noise barrier, since an even higher reduction could be achieved. A low-height noise barrier should be considered and further investigated since it actually reduces the levels of community noise and has good potential to protect pedestrians from collisions within an urban environment.