Study On Noise Reduction Effect Of Fully-enclosed Noise Barrier On High-speed Railway Bridge

The noise pollution resulted from high-speed railways produces a severe effect on both the environment and the living quality of residents along the line.It is necessary to take control measures especially when lines pass through the noise-sensative area.The noise barrier is a major way to control the traffic noise and can effectively shield the propagation of all kinds of noise sources.For the erect and semi-enclosed noise barrier which is open to noise,there is large amount of direct noise and serious diffraction phenomenon,so that the noise reduction effect is limited.The fully-enclosed noise barrier is often used for sections with higher noise reduction requirements.This thesis takes a bridge near the Jiangmen section on the Shenzhen to Maoming passenger line as an engineering example,on which the fully-enclosed noise barrier is mounted.Based on this,the theoretical and experimental investigations on the noise reduction effect of the fully-enclosed noise barrier are conducted,and the main contents and the results are as follows:(1)On the basis of the domestic and foreign relevant literatures,the study of present situation of noise barrier materials,structure and noise reduction prediction methods was reviewed,and statistical energy analysis(SEA)was introduced.(2)The full-scale model test of noise reduction characteristics of the high-speed railway fully-enclosed noise barrier was carried out.The two ends of the model were blocked by “steel plate + fiber glass board”.And the noise sources were simulated by loudspeakers,which played pink noise and measured train noise.The sound fields of three test sections were tested respectively,which included free field and two kinds of noise barriers.The noise reduction of the fully-enclosed metal noise barrier and concrete noise barrier is equivalent,and the reverberation effect of the latter is more significant.(3)Based on statistical energy analysis method,a SEA prediction model for fully-enclosed noise barrier was established.Assuming that the noise distribution is identical along the bridge,in other words,the noise is only lowered in transverse direction,a two-meter long section to simulate the noise propagation was selected.The problems of the source excitation,the calculation of barriers’ transmission loss,the loss factor in free field were solved.The noise reduction effect under the train noise excitation of two kinds of fully-enclosed noise barriers was analyzed based on the SEA model.(4)Based on train-track system coupling vibration analysis theory and finite element-boundary element method(FEM-BEM),the model of bridge-barrier to predict structural noise was established.The noise reduction effect of two kinds of fully-enclosed noise barrier was analyzed considering structural noise and train noise at the same time,and the effect of structural noise on the comprehensive noise reduction was discussed.Considering the influence of structural noise,the insertion loss of the fully-enclosed metal noise barrier and concrete noise barrier is reduced by 5~10 dB and 4~11 dB.However,there is little impact on A-weighting insertion loss.