When predicting the performance of noise barriers, vehicles are too often considered as point or line sources, neglecting their motion, body and reflective sides. Using sound absorbtive materials helps to reduce the sound reflections between vehicle body and noise barriers, and the interaction phenomenon is generally neglected. For reflective barriers, by contrast, this phenomenon is severe. Even when dealing with absorbtive barriers, for example, when they are close to the vehicles, the multiple reflections phenomenon becomes more important and can lead to a degradation of performance. Several designs can be considered in order to reduce these multiple reflections, e.g. absorbing materials, and inclined barriers. Even with classical sound absorbing materials, though reduced, these reflections can degrade the performance of barriers. One should consider this effect for the accurate design of barriers (materials and forms); 4D (3D+time) models are more appropriate and one should avoid to consider moving vehicles as fixed sources of coherent noise. Further investigations could be done with diffuse models for reflections instead of specular ones, or even a combination of the 2 effects.
How multiple reflections can a degradation of performance for noise barriers
Wie Mehrfachreflexionen eine Verminderung der Wirkung von Lärmschutzwänden verursachen können
1996
6 Seiten, 4 Bilder, 1 Tabelle, 7 Quellen
Conference paper
English
The performance of multiple noise barriers
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