Evaluation of barrier shapes by acoustic scale modeling

Abstract

A 116 scale-model study (using a high-voltage spark as a noise source, and modeling typical highway situations and materials) was undertaken to compare the acoustical performance of several common highway noise barrier shapes, namely, reflective thin walls, earth berms, and in particular, the combination of the two. It was suspected that additional scattering and absorption losses, which can occur along the top of an earth berm, may be lost if a low thin wall is erected atop the berm. A change of several dB due to the change in the barrier shape may be considered significant, since the field insertion losses of noise barriers are usually in the range of 5 to 10 dB A. Thin reflective walls and earth berms of the same height were found to be equally effective. Results also indicate that the acoustical performance of an earth berm (a) is not compromised by erecting a relatively low thin wall on its top, and (b) may be improved by placing sound absorptive material atop the berm.