Numerical study on the insertion loss of noise barrier for coherent/incoherent line source

概要

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The insertion losses of noise barrier for a coherent and an incoherent line sources were examined by the numerical analysis. We approximate that the coherent and the incoherent line sources are equal to a series of point sources that have the same and random phases respectively. And we examine the relation between the sound pressure level and the length of the series of point sources. In the case of the same phase sources, the diffracted sound waves from point sources located quite far a way from the receiving point are interfered each other and the contribution of them becomes quite small. On the other hand, in the case of the point sources of random phases the contribution of them becomes large compared with that of the sources located near by. Then the difference between the insertion losses in both cases is caused by the difference of the contributions of point sources located far from the receiving point. And the reason that the insertion losses in the cases of point source excitation in two dimensional space and coherent line source excitation in three dimensional space is caused by the fact that the insertion losses in latter case is mainly evaluated by the sources of same phase located quite near to the receiving point.
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