Effect of the open roof on low frequency acoustic propagation in street canyons

Abstract

a b s t r a c t This paper presents an experimental, numerical and analytical study of the open roof effect on acoustic propagation along a 3D urban canyon. The experimental study is led by means of a street scale model. The numerical results are performed with a 2D-Finite Difference in Time Domain approach adapted to take into account the acoustic radiation losses due to the street open roof. An analytical model, based on the modal decomposition of the pressure field in the street width mixed with a 2D image sources model including the reflection by the open roof, is also presented. Results are given for several frequencies in the low frequency domain. The comparison of these approaches shows a quite good agreement until f = 100 Hz at full scale. For higher frequency, experimental results show that the leakage, due to the street open roof, is not anymore uniformly distributed on all modes of the street. The notion of leaky modes must be introduced to model the acoustic propagation in a street canyon.

A Hybrid Model for Investigating the Effect of Scattering from Building Façade on Sound Propagation in Street Canyons

“…In this study, it has been proven to be accurate in relatively wide streets (15 to 25 m wide) and the middle-frequency range (500 and 1000 Hz octave bands). However, phase information might be crucial in narrow streets [45] and a low-frequency range [46].…”

Evaluation between Virtual Acoustic Model and Real Acoustic Scenarios for Urban Representation

“…They have centered on the complexity of the medium: irregular faces, interconnection with adjacent canyons, and a large variety of materials and boundary conditions. Moreover, a predominant characteristic of the urban environment is that it is open to the sky, and induces large radiative losses [5][6][7]. Much of the literature is focused on propagation in a single urban canyon [8][9][10][11][12][13].…”

Three-dimensional parabolic equation model for low frequency sound propagation in irregular urban canyons

“…5 These methods are efficient for high frequencies but fail in predicting wave effects such as interference and diffraction. Therefore, wave-based methods such as Equivalent Source Method, 6 FiniteDifference Time-Domain model, 7,8 Pseudospectral TimeDomain method, 9 Transmission Line Matrix, 10,11 and coupled Modal-Finite Element (Modal-FE), 12,13 have been applied for modeling the acoustic propagation in an urban canyon. Applications of this type of model are nevertheless mostly restricted by their expensive numerical cost, limiting their applications in an engineering context.…”