Sound Propagation in Complex Outdoor Situations with a Non-Refracting Atmosphere: Model Based on Analytical Solutions for Diffraction and Reflection

A model is described for sound propagation in outdoor situations with noise barriers, with a non-refracting atmosphere. The spectrum of the transfer function is computed by coherent summation of contributions of sound rays. The computation is based on analytical solutions for diffraction by a rigid wedge and reflection by a finite-impedance plane. Heuristic extensions of these solutions are used for situations with absorbing wedges, double wedges, and impedance transitions. The accuracy of the model is investigated by comparison with numerical computations with the boundary element method and with the parabolic equation method, and by comparison with experimental data. It is found that the model is accurate in various practical situations, including finite screens, rigid and absorbing wedges, rigid double wedges, two parallel screens, and impedance transitions, except at low frequency.