Wind tunnel experiments for the validation of numerical models for outdoor sound propagation. in Inter-noise

Since regulations concerning traffic noise are becoming more and more demanding, meteorological effects (turbulence, temperature and wind speed gradients) can no more be neglected in noise propagation prediction at long ranges. To validate numerical models such as Parabolic Equation approach or Boundary Elements Methods with modified Green’s functions, it is of high interest to collect experimental data obtained under controlled atmosphere. A measurement campaign has been performed in the wind tunnel of CSTB, Nantes (France). The objective of this experiment was to characterize the aerodynamic flow and the acoustic pressure during the sound propagation. A number of geometrical configurations (flat ground, embankment, with or without complex noise barrier, the ground surface being absorbing or not) and various wind profiles and turbulence intensities have been tested. A combination of traditional (hot wire probe) and recent (Particle Image Velocimetry, PIV) measurement techniques has been used in order to describe precisely the 2D wind speed field along the propagation as well as in the vicinity of the barrier where recirculation phenomenon occurs. For acousticians, experiments in wind tunnel are a good mean to improve their knowledge on outdoor sound propagation and to develop novel barrier shapes.