考虑声源非相干性的城市轨道交通全封闭声屏障降噪预测

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

以某轨道交通全封闭声屏障为研究对象,考虑简化线声源的非相干性,建立2.5维边界元衍射声场模型;通过现场沿线环境噪声测试,验证了该模型的准确性,并与相干源衍射声场预测结果比较;最后预测了在近场高层建筑附近,全封闭声屏障对近轨或远轨车辆噪声的降噪效果。研究结果表明,非相干线声源更符合城市轨道交通噪声源特性;对于轮轨噪声(315~1 000 Hz),全封闭声屏障在高层住宅建筑区域有显著的降噪效果,1/3倍频程插入损失最大为30.0 dB。对于低频噪声(50~250 Hz),全封闭声屏障会加重高层住宅建筑区域的声压级,使插入损失出现负值。针对高层建筑附近场点,全封闭声屏障的顶端拱形透光板对远轨车辆噪声有更为显著的附加降噪效果,大部分场点附加插入损失均高于5.0 dB。

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.