High frequency sound propagation in a network of interconnecting streets
Speaker: David Hewett, University College London
Title: High frequency sound propagation in a network of interconnecting streets
Abstract: We study the propagation of acoustic waves emitted by a time-harmonic source in a network of interconnecting city streets, in the high frequency regime where the wavelength is small compared to typical macro lengthscales such as street widths/lengths and building heights. We propose a new model for the acoustic energy propagation, which is based on a probabilistic modification of geometrical acoustics (ray theory), and represents the acoustic power flow along any pathway through the network as the integral of a power density over the launch angle of a ray emanating from the source. The model neglects interference between ray fields but takes into account the other key phenomena involved in the propagation, namely energy loss by wall absorption, energy redistribution at junctions, and, in 3D, energy loss to the atmosphere. The model predicts strongly anisotropic decay away from the source, with the power flow decaying exponentially in the number of junctions from the source, except along the axial directions of the network, where the decay is algebraic.