Impact of multiple reflections on urban acoustics

Understanding how the urban form contributes to noise is important for the successful acoustic design of cities. The amplification of sound is mainly due to the multiple reflections that occur between the high and parallel walls of urban canyons. This study explores the use of ray tracing at the urban scale through the measurement and simulation of three configurations. These are referred to as "1D", "2D" and "3D". Impulse response measurements performed at points located on the top of the facades show an increase of 6 dB for the "2D" case and 11 dB for the "3D" case. These results are consistent with ray tracing simulations. This kind of simulation is useful to determine the influence of the street aspect ratio on the sound level. Since specular reflections are related to geometry, a spatialized representation is proposed and discussed.