Boundary elements for noise barriers above an absorbing ground

The insertion loss (IL) of a noise barrier standing on an absorbing ground is investigated using the Boundary Element Method (BEM). The absorption of the ground is characterized by a finite complex impedance. The BEM formulation incorporates a tailored Green's function that satisfies the impedance boundary condition on the ground, therefore the ground is automatically taken into account and only the noise barrier must be discretized. The tailored Green's function can be described as a superposition of sources with complex positions and expressed as a line integral over an "imaginary axis". Such formulation is very suitable for a BEM implementation since the line integral exists for all kind of impedances and converges faster than other formulas. In the present paper, the influence of the type and magnitude of the ground impedance on the shielding properties of the barrier is studied in detail. The noise barrier itself is considered rigid.