Urban Background Noise Mapping: The General Model

Abstract

Surveys show that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. However, current practice in noise prediction often underestimates the noise levels at a shielded façade. Multiple reflections between façades in street canyons and inner yards are commonly neglected and façades are approximated as perfectly flat surfaces yielding only specular reflection. In addition, sources at distances much larger than normally taken into account in noise maps might still contribute significantly. Since one of the main reasons for this is computational burden, an efficient engineering model for the diffraction of the sound over the roof tops is proposed, which considers multiple reflections, variation in building height, canyon width, façade roughness and different roof shapes. The model is fitted on an extensive set of full-wave numerical calculations of canyon-to-canyon sound propagation with configurations matching the distribution of streets and building geometries in a typical historically grown European city. This model allows calculating the background noise in the shielded areas of a city, which could then efficiently be used to improve existing noise mapping calculations. The model was validated by comparison to long-term measurements at 9 building façades whereof 3 were at inner yards in the city of Ghent, Belgium. At shielded façades, a strong improvement in prediction accuracy is obtained.

Analysis of Technical Criticalities for GIS Modelling an Urban Noise Map

“…As already underlined in the discussion, the data for the internal construction of the indicators (Weber, 2011) are strongly dependent on the number of people in the highest noise classes. It is believed that in this yearly mapping of Palermo, information pertaining to the most critical cases was given, not taking into consideration less noisy roads, which, in a global vision, would diminish the overall effects of traffic noise (Wei et al 2014).…”

Corrigendum to Urban Background Noise Mapping: The General Model

“…A few typos in [1] were found and corrected in the current corrigendum. When applying the Hurwitz-Lerch transcendent, the power of the reflection coefficients ρ s and ρ r should be 6 instead of 2.…”

Simplified analytical model for sound level prediction at shielded urban locations involving multiple diffraction and reflections

“…The later means that this approximation can lead to big errors when X is close to 0. To avoid this singularity, the Fresnel Integrals are approximated by 15 :…”

“…The diffraction formula used in this study is essentially based on Pierce's diffraction theory 3 , where the Fresnel Integral is approached by trigonometric functions for efficient evaluation, and parameterized for typical urban environments as discussed by Wei et al 15 .…”

“…After the Introduction, the simplified diffraction formulas as previously presented in Wei et al 15 are summarized in Sections II. A and II.…”