Propagation of sound over grassland and over an earth barrier

A model for the calculation of effects of ground and a screen or a wedge shaped barrier on the transmission of sound has been tested by comparing calculated transmission losses with losses measured in real situations. With the model presented in this paper, the effect of a homogeneous ground with a finite or an infinite impedance, the effect of diffraction at a discontinuity in the impedance of the ground (e.g., the transition between road surface and adjacent grassland), and the combined effect of ground surface and a barrier with a finite or an infinite surface impedance can be handled. The incorporation of the effects of a discontinuity in the impedance of the ground and of the finiteness of the height of a barrier led to an additional improvement of the agreement between calculated and measured transmission losses.