Abstract
This study employed a computer program to identify the insertion loss degradation of barrier due the reflection. The mathematical theories of single barrier prediction are based on Maekawa prediction [1], which predicts the attenuation produced by the barrier as a function of geometry and frequency. The single image source concept was used for estimating the reflection effect of the second barrier.
A scale model of a scale 1:20 and a line source made of small speakers were used to verify the accuracy of the computer program. The results from the program agree well with those of scale models. The results show that the region of where the illuminated zone of the virtual source and the shadow zone of the primary source overlap (Ys1 < Y < Ys) is the critical region of noise degradation. Thus, the image source model with a virtual barrier is a very useful and straight-forward tool for the design of parallel barriers. Four barrier design parameters have been analyzed; sound source position, barrier height, distance between parallel barriers and the usefulness of absorptive material applied at the second barrier.
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