THE PERFORMANCE OF MULTIPLE NOISE BARRIERS

A numerical model, based on boundary element techniques, was used to solve the acoustic wave equation in two dimensions, in order to study the performance of various configurations of road traffic noise barriers. The mean insertion loss for a broadband road traffic noise source over a range of receiver positions behind the barrier is used as a measure of efficiency. Barriers comprised of several parallel screens on the same side of the road are evaluated in terms of number and separation, and are compared with a single screen and results of experimental modelling. The effects of placing absorbent treatment on the surfaces of the screens and on the ground surface are also considered. Multiple-edged barriers with a single foundation and multiple earth mounds are discussed, as well as effects relating to multiple reflections of sound from high vehicles and from parallel screens on the opposite side of the road.