Study on prediction of road traffic noise around tunnel entrance

摘要

Prediction of road traffic noise in the vicinity of a road tunnel entrance has been one of the most difficult problems. The built-up noise in the tunnel radiates towards outside the entrance. A practical calculation model for this noise radiation is developed in this paper, which is based upon a sound energy balance inside the tunnel. Two imaginary sources are assumed. One is a point source which represents a direct sound from a vehicle in the tunnel. The geometrical location of the imaginary point source is determined by the position of the vehicle and by a new parameter "a" that is related to the acoustical properties of the inside walls. The second is a surface source which represents residual sound with multiple reflection between the walls of the tunnel. This source is specified at the tunnel entrance. Results of a sound level (L{sub}(Aeq)) measurement at a highway tunnel shows good agreement with an accuracy of less than 3 dB between the calculated and the measured. It is shown that this model is applicable to road traffic noise simulation at a tunnel with a noise control design by absorptive treatment on the walls.