Scale model investigation of factors affecting the performance of roadside noise barriers.

Abstract

Besides numerical models, another way to model complex environments is using physical reduced-scale models. This project used scale models to study several factors which may influence the performance of roadside noise barriers. One is the barrier absorption. Making the barrier sound absorptive decreases reflections and may decrease amplification between parallel barriers. The other is tree foliage growing near the barrier. Tree foliage may scatter sound into the shadow zone behind the barrier, increasing noise levels and decreasing the insertion loss. Tree foliage may also attenuate sound that would normally be diffracted into the shadow zone, actually increasing the insertion loss. A 1:31.5 scale model was created in an anechoic chamber to test the effects of these two factors. Excess attenuation measurements were performed to choose scale model materials, which accurately represent full scale surfaces. Parallel barriers were modeled with a reflective surface and their IL's were measured for different configurations of absorptive covering. IL's of single barriers were measured both with and without scale model trees placed either in front or behind them. The results are compared to previously performed field test measurements.

Compliance and vegetated-barrier acoustical testing in a purpose-built sound-transmission suite

“…It certainly absorbs significantly more sound than a typical reflective noise barrier. However, it is apparently not as absorbent as commercially-available absorbent conventional barriers [7].…”