ABSTRACT
Noise reduction by barriers is a popular method for mitigating the effects of noise from transportation. Near a highway, railway or airport, the receiver can be shielded by a barrier, which intercepts the line-of-sight from the noise source. As long as the direct transmission of sound through the barrier is negligible, the acoustic field in the shadow region is mainly dominated by the sound diffracted around the barrier. Themany different types of barriers include a ‘normal’ straightedge barrier, a top-bended or ‘cranked’ barrier, an inclined barrier, a louvre barrier and a barrier with multiple edges. To design noise barriers with optimum acoustic performance, it is important to have accurate prediction schemes for calculating the sound reduction by barriers. The aims of this chapter are
1 to introduce the basic principles of the diffraction of sound by noise barriers and identify the important parameters,
2 to discuss both analytical and empirical models for studying the acoustic performance of noise barriers,
3 to determine the degradation of performance due to presence of gaps in barriers,
4 to explore the effectiveness of a barrier in screening a directional source and 5 to investigate the consequences of assuming a fixed source spectrum when
calculating the performance of noise control elements such as barriers.
