EFFICIENCY OF SINGLE NOISE BARRIERS

A numerical model is described which enables the sound field in the region of outdoor noise barriers to be calculated by using the boundary element method. The non-uniqueness of solution of the method, producing unreliable results in some conditions, is discussed. The model can be applied to barriers of arbitrary cross-sectional shape and arbitrary distribution of surface cover. The model is two-dimensional, but results are shown to agree well with those obtained for the three-dimensional problem of propagation from a point source over a noise barrier of infinite length. The model is used to compare the efficiency of a wide range of constructions of single noise barriers of different height, cross-sectional shape and surface cover. The effects of the ground cover are also considered. Comparison is made by examining spectra of the insertion loss of the barriers, and also broadband insertion losses for a source with a characteristic A-weighted road traffic noise spectrum. Single-figure estimates are presented of the relative efficiency, in terms of insertion loss, in the deep shadow zone, of a wide range of barrier configurations. © 1991.