Noise Reduction Prediction of a Fully-Enclosed Sound Barrier in Urban Rail Transit Systems Considering Incoherence of Sources

Abstract:

A 2.5-dimensional boundary element method（BEM） diffraction sound field model was established， by taking a rail transit fully-enclosed sound barrier as the research object and considering the incoherence of the simplified linear sound source. The accuracy of the model was verified by field noise tests along an urban line， and the prediction results were compared with those of the coherent source diffraction sound field. Finally， at the positions of the high-rise buildings along the line， the noise reduction effects of the fully-enclosed sound barrier on the passing noise of near or far rail vehicles were predicted. The results show that the incoherent line sources are more in accordance with the characteristics of urban rail transit noise sources. The prediction results of their diffraction sound field are more consistent with the measured results. For wheel-rail noise （315 to 1 000 Hz）， the fully-enclosed barrier has a considerable reduction effect at the area of the high-rise buildings， with the maximum 1/3 octave band insertion loss of 30.0 dB. For low-frequency noise （50 to 250 Hz）， the fully-enclosed barrier enhances the sound pressure levels at the area of the high-rise buildings， leading to negative values of the insertion losses. For the receivers near high-rise buildings， the top-arched transparent panels of the fully enclosed sound barrier have a more significant additional noise reduction effect on the passing noise of far rail vehicles， and the additional insertion losses at most receivers are higher than 5.0 dB.