Acoustic Design,Optimization And Experimental Study Of High-speed Railway Sound Barrier

The rapid development of high-speed railway in China has brought convenience and comfort to people's travel.At the same time,the railway line through towns brought serious noise to the surrounding environment.Acoustic barrier is one of the main methods of high-speed railway noise isolation,and can effectively block the propagation of high-speed noise sources.But,the high-speed operation of train also poses a danger to the safety of sound barrier.Between high-speed train and sound barriers,the air is in a semi-enclosed space,and the passing of high-speed train with a strong air disturbance affects the interference of noise barrier to use security.For high-speed railway noise barrier,the noise reduction performance is closely related to its structure,sound absorption material used,train operation speed,sound source distribution,frequency spectrum characteristics.High-speed train noise in all the height of the train has the frequency bandwidth.The past research on the noise reduction performance of high-speed railway sound barrier neglected the sound source distribution and the effect of the frequency spectrum characteristics of the sound barrier on noise reduction,and didn't considered the multiple reflection of the noise among the car-bodies,the sound barrieries and the track.Therefore,there is some difference between the theoretical model of the noise reduction performance analysis of high-speed railway sound barriers and the structural characteristics of the sound barrieries.With the train running speed increase,air-flow noise makes a large instant pressure difference between the sound barrier panel and its back plate,resulting in the vibration noise,instability and fatigue damage of the barrier.In this environment,new requirements are proposed for the design of high-speed railway sound barrier.The sound barrier structure should be able to release the pressure of air flow,and also have good noise reduction.Therefore,the acoustical design,optimization and experimental study of high-speed rail sound barrier are further to be carried out.The paper work was fund by the National High Technology Research and Development 863 Plan "Composite Noise Characteristic Analysis of High-Speed Railway Noise Barrier and Mechanism of Noise Reduction of Noise Barrier with Deloading(2011AA11A103-4-2)","Key Science and Technology Research for Safe Operation of High-Speed Train(50821063)" and "Science and Technology Plan Projects of Sichuan Province(2010 JY0070)".The main research work carried out has the following aspects:(1)The test and analysis system of noise source of high speed train was established,and the corresponding numerical analysis program was developed.The system includes the beamforming acoustic source recognition system and the standard point noise test system.The beamforming source recognition system uses the "delay and sum" algorithm.The standard noise test is based on IS03095-2015.(2)The acoustic analysis model for high-speed railway outdoor noise is further improved.The model uses the two-dimensional boundary element method,consideres the geometric boundary condition of the train operation and the multiple noise reflection between barrier-track-train-body.According to the characteristics of sound sources and their distribution,the main sources of high-speed railway are established.(3)The design principle and the performance evaluation index of subtraction sound barrier were proposed.(4)The computational model of unit plate isolation of the acoustic barrier with deloading was established.The model adopts acoustic finite element method.In the model,acoustic finite element grids were used to model the hole clearances and vocal cavities of the barrier.Acoustic barrier unit board is porous sound-absorbing material.It was assumed that the acoustic pressure is continuous between the unit plate and the vocal cavity.In the initial boundary conditions,it was assumed that the sound barrier has smooth sound reflection surfaces in the train operation direction,the inlet boundary has no displacement,the outlet has no reflection boundary condition,and the initial air flow velocity is zero.(5)Based on the ISO140-3 and GB/T 19889.3,the performance of the acoustic insulation of acoustic barrier was analyzed by the sound pressure method.(6)An analysis model of transmission acoustic propagation of acoustic barrier with deloading was established,and the definition of sound insolation in this model was given.The model uses the rectangular spoke.One side of the sound barrier is regarded as a free field,and the other side is treated as a sound room.The sound source was assumed to be a line source that conforms to the vertical incidence of high-speed railway.According to the transmission law of sound,the sound effect of the acoustic barrier with deloading was determined.Using the above numerical model,the above test and analysis system for high-speed railway noise barrier carried out the research on the sound intensity of high-speed railway noise source,universal acoustic noise barrier properties,noise characterstic of the sound barrier with deloading.(1)Research on the intensity and distribution characteristics of the noise sources of high-speed railway.A beamforming acoustic source recognition system was used to test and analyze the characteristics of the noise sources and their spectra.At different speeds,the noise source energy is distributed in the direction of the train's height.The standard point noise test system is used to analyze the distribution characteristics of sound field points,the time history of the noises at the standard points and the frequency characteristics of sound pressure.(2)The analysis model of the outdoor noise of high-speed trian was improved.The model was used to investigate the intensity of high-speed railway noise source influencing on the sound field,and got site sound pressure changing with the operation speed,as well as the contribution of main noise sources.The influence of sound absorption coefficient,acoustic barrier structure parameter,and its top device on the distribution of sound field and the characteristics of field point spectrum were analyzed.The noise reduction of the top device was analyzed,and the optimal structure was proposed.(3)Six kinds of structure design schemes of sound barrier with deloading were put forward.Through the contrast analysis of their deloading characteristic,an detailed investigation into theeffect of the opening rate of the end plate structure and its leaf thickness on their deloading performace were carried out to in order to provide the good references for structural optimization and scheme selection.(4)The model of cell plate isolation was established.Using this model,the effect of different material parameters and structural parameters on the sound insulation performance of the acoustic barrier was analyzed.The effects of the absorption material and structural form were investigated and analyzed and also the unit plate noise isolation was tested.According to the sound insulation curve,the measures to further improve the sound insulation performance of the cell plate were proposed and the deloading structures suitable for the noise reduction of high-speed railway were selected.(5)Using the analysis model for high-speed railway outdoor noise and the analysis model for sound propagation law of reloading noise barrier anylzed the noise isolation performance of the two types of the sound barriers with deloading,respectively,optimized their structure form,and investigated the influence of their structure form on their insert loss.(6)Considering the reloading,the noise reduction,the site installation conditon and the safety in service,the best structure was determined and its acoustic performance was assessed.The acoustic pressure distribution on the field site of the reloading barrier was analyzed,and the relationship between the sound pressure and the train operation speed was found.The noise reduction effect of different height of the sound barrier was studied,and the influence of spectral pattern was analyzed.Finally,the effect of train speed on noise reduction of the acoustic barrier was investigated,and the maximum speed range for the reloding sound barrier was proposed.