Parameter study of sound propagation between city canyons with a coupled FDTD-PE model

Abstract

A parameter study is performed for the case of two-dimensional sound propagation from a (source) city canyon to a nearby, identical (receiver) city canyon. Focus was on sound pressure levels, relative to the free field, in the shielded canyon. An accurate and efficient coupled FDTD-PE model was applied, exploiting symmetry of the source and receiver canyon. With the proposed calculation method, simulations were necessary in only half the sound propagation domain. The shielding in the receiver canyon in case of a coherent line source was compared to the shielding by an incoherent line source, by means of sound propagation calculations in a number of 2D cross-sections through source and receiver. It was found that the shielding is rather insensitive to the width-height ratio of the canyons. The presence of diffusely reflecting façades and balconies lead to an important increase in shielding compared to flat façades. Rigid façades yield significantly lower shielding compared to partly reflecting façades. Effects of a moving atmosphere were modeled in detail. Shielding decreases significantly in case of downwind sound propagation when comparing to sound propagation in a non-moving atmosphere. Refraction is the most important effect in the latter. In case of upwind sound propagation, turbulent scattering plays an important role and the shielding is similar to the one of a non-moving atmosphere for the parameters used in this paper. The combination of effects, as is shown by some examples, is in general not a simple addition of the separate effects.

Using natural means to reduce surface transport noise during propagation outdoors

“…Consequently, this concept has become part of the noise policy in a number of European cities [114]. Therefore, potentially quiet areas, like urban courtyards, have been studied in detail [115][116][117][118][119][120][121][122]. Although courtyards are often strongly shielded from direct exposure to road traffic noise, many of such places were found to exhibit noise levels that are too high to function as quiet areas [123].…”

“…Therefore, mitigation measures to reduce noise levels in urban courtyards are required to fully benefit from access to quietness. The potential of various measures has already been explored [115,119,124,125]. It was found that both façade and roof treatments can contribute significantly to the mitigation of noise from road traffic outside the courtyard.…”

“…It was found that both façade and roof treatments can contribute significantly to the mitigation of noise from road traffic outside the courtyard. Regarding façade treatments, both the effect of increasing absorption and diffusivity of façades was shown to reduce noise levels in the courtyard [115,119,125]. However, road traffic noise could not only reach the courtyard by propagation over roofs, but also through openings in the building blocks forming the courtyard.…”

“…[115,119] showed that applying façade absorption in the source canyon is especially interesting to achieve noise abatement in an adjacent canyon. In Ref.…”

The potential of building envelope greening to achieve quietness

“…1 a). The latter is responsible of building up a diffuse sound field in the canyons, which could influence the effectiveness of treatments [38][42]. All buildings have similar façades.…”