A 3D complex urban sound propagation benchmark case

Abstract

Predicting sound propagation in the dense urban fabric is challenging as it involves multiple and higher-order reflections, both specular and diffuse in nature, diffraction around complex objects like building edges and roofs, and atmospheric effects especially relevant at non-directly exposed locations. Over the last decades, there has been a continuing interest in enclosed courtyards, a micro-environment with the potential to offer human restoration in a busy city. Also roofs are increasingly being designed as outdoor spaces. The sound exposure in such zones could be especially challenging to predict. To gain more understanding in the related physics and accuracy of prediction schemes, a 3D urban benchmark case is presented, consisting of 4 building blocks with a fully symmetric geometry. Receivers and acoustic sources are positioned in the streets, on the roofs, and in the courtyards. Simulations with the reference finite-difference time-domain technique show pronounced differences in the time responses, and allow assessing the impact of including (geometrical) façade details. Additional simulations show the impact of openings from within the streets towards the courtyards. The simulation results allow checking the accuracy of sound propagation models and their simplifications.