Session NN. Noise IV: Outdoor Sound Propagation: A Special Workshop

The nature of sound propagation in the outdoor environment is an important consideration in the prediction of the noise impact from highways, airports, and railroads. Current noise prediction methods do not adequately account for the manner in which sound is attenuated with distance over open ground or through vegetation. A considerable amount of research has been conducted on outdoor sound propagation; however, a review of the literature shows that there are large discrepancies between various researchers for both open ground propagation and for propagation through forests. The results of theoretical analyses for the open ground case vary, depending on the boundary condition assumption. The assumption of a locally reacting ground surface results in a solution which appears to be valid; however, when the ground is treated as an elastic medium a different result is obtained. An additional deviation is obtained when the ground is treated as a layered elastic medium. It appears that the results of the variou...