Abstract
KEYWORDS
Noise barrier, Equivalent sources method (ESM), Insertion loss, Green function, Optimization)
ABSTRACT
Noise barriers are commonly used for noise reduction near highways, railways and other noise sources. Tall barriers are generally more effective, but their appearance is often not very aesthetic. Moreover, tall barriers often obstruct the view from dwellings. Therefore, there is a need to make low-height noise barriers as efficient as barriers of normal height. A large number of noise barrier shapes have been tested during the last decades (see for instance (1,2)) and some attempts of using active noise control in connection with noise barriers have also been made (3,4). The work presented in the following focuses on the optimization of low-height barriers. The main idea is to minimize the sound pressure at a given surface or domain behind the barrier, irrespectively of the barrier’s shape or surface impedance. Both shape and impedance will be a result of the optimization procedure. The equivalent sources method is used to calculate the diffracted pressure field behind a noise barrier. In principle this method is based on the idea of approximating a sound field outside an enclosure by sources located inside this volume. These so called “equivalent sources” can be of any type as long as they are solutions to the wave equation (see (5)). The strengths of these sources are objects to the optimization procedure. In (6) this method is used to calculate the diffracted pressure field behind a noise barrier and boundary conditions.