城市轨道交通直壁式声屏障车致振动声辐射机理

Vibration-acoustical Radiation Mechanism of Straight-wall Noise Barrier Induced by Vehicle in Urban Rail Transit

以往针对城市轨道交通运营时引起的线路结构噪声的研究主要集中在桥梁结构振动辐射噪声,而对于在高架线路上减小轮轨等线上噪声对沿线居民的影响常采用的措施主要为在线路两侧安装声屏障。但在列车经过高架线路时车致振动也会传递至声屏障,进而引起声屏障结构的振动向外辐射声波,同样会对沿线居民的生活环境带来影响。通过建立列车-轨道-桥梁-声屏障动力学模型及声屏障声学边界元模型,对2.5 m直壁式声屏障的车致振动噪声及其机理进行了研究。研究结果表明:在研究声屏障车致振动声辐射问题时需要建立不同单元组合的三维有限元模型,不能将声屏障的所有部件简单考虑为板壳单元;直壁式声屏障结构所有部件的振动形式基本呈现出纵向上的正弦式弯曲振动,其中通透隔声板的振动最为剧烈,呈现水平方向上的显著局部振动特性;列车通过时声屏障结构在其固有频率附近产生明显的共振现象,并具有很强的声辐射能力,其中通透隔声板是其声辐射最为主要的贡献者;直壁式声屏障对线路两侧沿线的声环境影响较大,主体趋势呈现出在水平方向上辐射声波,从而明显影响铁路沿线的声环境。

The existing research on structural noise caused by urban rail transit operations mainly focused on the noise radiated by the bridges.In order to reduce the adverse effects of line noise,such as wheel-track noise,on residents along the elevated line,the noise barriers are usually installed on both sides of the line.However,when a train passes the elevated line,the vibration induced by moving train loads will be transmitted to the noise barrier which will vibrate and radiate the sound waves,bringing about negative effects on the acoustic environment along the line.Therefore,a train-track-bridge-noise barrier coupled dynamic model and the acoustic boundary element model of noise barrier were established to study the vibration noise and mechanism of the 2.5 m straight-wall noise barrier.The results show that the establishment of three-dimensional finite element models with different elements is required to study the vibration sound radiation of the noise barrier,and all components of the noise barrier cannot be simply considered as shell elements.The vibration modes of all components of the noise barrier present longitudinal sinusoid bending mode,of which the vibration of transparent sound board is most severe,showing obvious local vibration characteristics in horizontal direction.When the train passes,the noise barrier produces resonances at its natural frequencies,with strong sound radiation ability.The transparent sound board plays a key role in the sound radiation of the noise barrier.The straight-wall noise barrier has a greater impact on the acoustic environment along both sides of the line,mainly radiating sound waves in the horizontal direction.