Prediction Of Noise Reduction Effect Of A Near-rail Barrier For Inter-city Railways

With the rapid development of urban agglomeration in China,inter-city railway has gradually become an important means of transportation to meet the needs of fast travel between cities.While the inter-city railway is convenient for people to travel,the noise generated by its operation process brings adverse effects to the residents along the line.Therefore,the study of noise control outside the vehicle is very important.As for a common technology in noise control,the noise barrier has been widely used.Considering the need for unshielded scenery and sight,the near-rail barrier has gradually attracted people's attentions in recent years.In this thesis,the following aspects of work are mainly carried out around the near-rail noise barrier to control the noise outside the inter-city train.(1)The application of near-rail barrier around the world and the research of resonance sound absorption barrier are summarized.The significance of this study is clarified.(2)Based on fiels test,the time history and spectrum characteristics of the noise at the outfield points of inter-city trains are analyzed.Then the noise characteristics outside the train are analyzed.The sound sources of 200 km/h inter-city trains mainly distribute in the area under the vehicle.The proportions of sound power in the area under the vehicle,body and roof are 89.0%,6.4% and 4.6%,respectively.The vertical and longitudinal distribution characteristics of the sound source are mainly studied.The sound sources of intercity trains at different running speeds are compared.When the running speed increases from 160 km/h to 280 km/h,the sound power levels of under-car,body and roof areas increase by 4.9 dB,8.0 dB and 8.1 dB,respectively.At the same time,the proportion of sound power in the roof and body area increases gradually,while the proportion of sound power in the area under the car decreases gradually.(3)The boundary element method is used to establish the simulation and prediction model of the exteral noise of the inter-city train.The noise reduction effect of C-type near-rail noise barrier and that of vertical near-rail noise barrier are compared and analyzed,and the factors affecting the noise reduction effect of C-type near-rail noise barrier are studied.Among the structural factors affecting the noise reduction effect of C-type near-rail noise barrier,improving the height of the noise barrier is the most effective way.As the height increases from 0.7 m to 1.4 m,the insertion loss of C-type near-rail noise barrier at the standard point outside the vehicle increases by 1.1-5.8 dB.The effect of noise reduction is related to the location of evaluation points.With an increase of speed,the noise reduction effect of C-type near-orbit noise barrier is gradually weakened.(4)The Helmholtz resonator is used to further optimize the C-type near-rail noise barrier.The noise reduction effect of resonant sound absorption barrier is studied for 630 Hz significant frequency band,and the influence of resonator structure,arrangement mode and arrangement density is further investigated.The results show that the resonance sound absorption barrier can reduce the noise in the preset frequency range.For the standard points outside the vehicle,the installation of Helmholtz resonator can make the noise reduction effect of C near-rail noise barrier up to 11.0 dB.