Noise abatement schemes for real life shielded urban environments: an initial investigation of absorption treatments.

Urban areas shielded from direct road traffic noise are of a high value with respect to effects of noise on health and well-being effects. Since many distant sources contribute to the sound pressure levels at these areas, like inner yards, reducing the levels could be necessary. In this paper, two such shielded environments in Gothenburg have been selected for a numerical investigation of noise abatement schemes. Thereby, it is of importance that a realistic source has been used and that the modeled reference situations are close to the selected environments. The study is executed using a wave based numerical model for parallel street canyons, the 2.5 dimensional Equivalent Sources Method. In this preliminary study, façade absorption treatments and a change of the ground impedance at the shielded sides have been investigated. As a result, a realistic change of façade absorption coefficients can lead to a reduction of 5 dB(A), and a change of the ground impedance from that of asphalt to grass to a reduction of 3 dB(A). The reduction is largest for the lowest receiver positions in the shielded canyon. When the dominating source is located in a street canyon, absorption treatments in the street canyon are more effective than in the shielded canyon for receivers at a higher position than the source