| Wave based solutions of noise barrier geometries accurately model the complex direct, reflected and diffracted sound field interactions. However, these solutions are very computer intensive and thus are not practical as a design tool. Improved diffraction based methods, that include phase, now yield wave-like accuracy with trivial calculation times. Extensions of these methods are made to consider two dimensional geometries, parallel barrier geometries, the effect of finite ground impedance and the consideration of three-dimensional coherent and incoherent line sources. Good agreements were observed with both finite element and boundary element models. These results, however accurate, typically over-predict the actual performance of noise barriers, because atmospheric effects such as wind, temperature gradients and turbulence have not been considered.;To overcome this limitation, a new acoustic modeling tool is proposed that combines an improved diffraction-based sound barrier performance model with a heuristic atmospheric model. Comparisons with the Parabolic Equation (PE), a wave based technique, show good agreements and preliminary applications of this model yield the expected sound barrier performance degradation due to the acoustic medium non-homogeneity. |
