城轨高架环境噪声特性与不同频段能量

测试了某城市地铁1号线一期高架线路普通整体道床无声屏障和道床垫式浮置板道床全声屏障区段的桥侧环境噪声, 分析了桥侧各测点的A计权总声压级与1/3频程线性声压级, 绘制了线性声压级云图, 研究了各频段噪声能量比例。分析结果表明: 道床垫式浮置板道床全声屏障能有效降低噪声源强处与桥侧环境噪声, 降噪效果、能量分布与频段和测点位置有关; 在桥面高度相近的测点, 降噪效果随距线路中心线距离的增大而减小, 而在近地面的测点, 降噪效果随距线路中心线距离的增大而增大; 降噪效果在中高频段明显大于低频段; 在1/3频程中心频率为20.0~31.5 Hz时, 距离线路中心线55.0 m处, 道床垫式浮置板道床全声屏障区段的线性声压级较普通整体道床无声屏障区段大0.82~6.96 dB; 在普通整体道床无声屏障区段, 在高出地面1.2、9.8 m处, 噪声能量以低于200 Hz为主, 在高出地面11.3 m处, 噪声能量以250~400 Hz为主, 在高出地面12.8 m处, 噪声能量以400~1 000 Hz为主; 在高出地面11.3 m处与200 Hz以下范围内, 普通整体道床无声屏障和道床垫式浮置板道床全声屏障区段的噪声能量持平; 在道床垫式浮置板道床全声屏障区段, 低于200 Hz的桥侧噪声能量较高, 因此, 建议根据高架桥旁敏感点的具体位置采取针对性减振降噪措施, 并重点关注低频噪声失去中高频噪声的遮蔽后尤显突出的问题。 

Characteristics and energies in different frequency bands of environmental noise in urban elevated rail

The environmental noises of bridge side of the first stage elevated line of Metro Line 1 in a city were compared and tested, where the common monolithic track beds without sound barrier and the slab mat track bed with closed sound barrier were used separately.The Aweighted total sound pressure level and 1/3 octave linear sound pressure level of each measuring point on the bridge side were analyzed.The linear sound pressure level cloud diagrams were plotted.Noise energy ratio in each frequency band was studied.Analysis result shows that the slab mat track bed with closed sound barrier can effectively reduce the noise at the noise source strength point and the environmental noise on the bridge side.The noise reduction effect and energy distribution are related to the locations of frequency band and measuring point.At measuring points of similar bridge height, the noise reduction effect decreases with the increase ofthe distance from the centerline of line, while the noise reduction effect at the near-ground point increases with the increase of the distance from the centerline of line.The noise reduction effect of slab track mattress with closed sound barrier is significantly higher in mid-high frequency range than in low frequency range.When the center frequency of the 1/3 octave is 20.0-31.5 Hz, 55.0 m away from the centerline of line, the linear sound pressure level of slab mat track bed with closed sound barrier is 0.82-6.96 dB higher than that of common monolithic track bed without sound barrier.In the section of common monolithic track bed without sound barrier, the noise energy is mainly below 200 Hz above the ground of 1.2 and 9.8 m, in 250-400 Hz above the ground of 11.3 m, in 400-1 000 Hz above the ground of 12.8 m.Above the ground of 11.3 m, below 200 Hz, the noise energies are nearly equal between the common monolithic track bed without sound barrier and the slab mat track bed with closed sound barrier.In the slab mat track bed area with closed sound barrier, the noise energy below 200 Hz at the bridge side is higher.Therefore, it is recommended to take targeted measures for vibration reduction and noise reduction according to the locations of sensitive points beside the elevated bridge, and to focus on the problems that low frequency noise appears prominently after it has lost the shielding of medium and high-frequency noise.