Prediction of sound radiated from tunnel openings

Road or railway tunnels are taken into account in noise prediction programs with the traffic flow ending at the tunnel mouth. The sound radiated from inside the tunnel through the tunnel mouth into the environment is calculated using an additional point or area source at the position of the tunnel opening. Some investigations have been published where the source strength of the radiating tunnel mouth has been calculated from analytically derived propagation relations inside the tunnel. In the meantime sound propagation inside rooms can be modelled more precisely even for complex environments, where the basic algorithms have been selected and improved based on measurements in more than 150 rooms and halls. These techniques have been standardized and in the meantime after about 8 years of experience with the application of these strategies they form an experimentally well established and computer based method that can be used to solve many of these special problems. The procedure is used as a part of an integral approach to calculate the noise radiated from tunnel openings. It can be used for different and even complex configurations and may help to integrate this very special noise source in environmental modelling for noise calculation.