A note on noise propagation in street canyons

Abstract

The current study examines the propagation of sound in street canyons with geometrically reflecting surfaces. An image source method is a popular numerical model to estimate the propagation of sound energy in a street canyon. This numerical model calculates the total sound energy received at a field point by summing the contributions from individual image sources incoherently. The discrete image source model is generalized by replacing rows of point sources with their respective line sources. An integral formulation is derived, which can be evaluated exactly to give a simple analytical solution. The expression permits rapid computations of the sound energy due to a point source placed in a street canyon. The transient sound energy at a receiver point is also examined. It has been demonstrated that the transient sound energy can be expressed in terms of a standard exponential integral. The Schroeder integration method is then used to calculate the reverberation times, which allow a straightforward assessment of the acoustic environment in street canyons. Indoor and outdoor experiments were conducted to validate the proposed integral formulation. The analytical formulas were also compared with numerical results based on the standard image source method and with published experimental data.