Research On Noise Source Identification And Control Technologies Of High-speed Railway

Large-scale construction and operation of high-speed railway has not only been providing strong support for social and economic development,but also bringing some impacts on environment.At present,exterior radiation noise and interior noise from some of existing Electric Multiple Units(EMU)trains and environment noises from high speed railway in China exceed requirements of evaluation indicators of relevant stantdard,so it is neccessary to conduct research on noise source identification and control technology in high-speed railway.Exterior radiation noise from EMU is a complex noise source featured by high speed movement in large-scale open space,wide frequency and multiple sound sources couplded,and there were factors in existing high speed railway including low resolution caused by big width of main lobe and side lobe jamming in identification algorithm of noise sources,annihilation of noise sources caused by Doppler effect,false sounde sources deviating from actual sound sources and other factors that affect accuracy of identification,and besides,it was impossible to effectively identify different noise sources at the same location,so that it was hard to put forward specific control measures.In addition,there were only limited measures for vibration and noise reduction and the absorption and sound insulation performance and application effect of sound barrier materials were limited for low and medium frequencies in high speed railway in China.In order to improve the accuracy of the noise source identification of the motion sound source,this paper make an optimization algorithm based on the fast Fourier transform and non-negative least squares(FFT-NNLS)for the identification with beamforming method.The results showed that this method reduces the main lobe of the array and eliminate sidelobe lecel effectively.Also,the resolution of sound source recognition was improved.The doppler effect of the motion sound source was modified based on the time domain transform,which effectively improved the sound source annihilation and false sound source phenomenon caused by doppler frequency shift.In this paper,a high performance microphone array was designed to meet the noise source identification of high-speed railway by comparing the characteristics of the point propagation function of different kinds of array.In this paper,the noise source identification test of high-speed railway was carried out by using the optimized algorithm.The test result showed that the sound source was mainly distributed in bogie,headgear and pantograph and the contribution of the lower part of the train was still dominant at the speed of 350km/h.In addition,the calculation method for wheel and rail radiation noise based on wheel vibration response and selective acoustic intensity technology was constructed,this method can be used to signal separation for mixed noise source in the wheel and rail area of high speed railway.The results showed that the external noise of high-speed railway vehicle was mainly the rolling noise at the speed of 200km/h,and the rolling noise of the wheel was about half of the total noise energy at the speed of 300～350km/h.Due to the fact that the noise contribution in the wheel and rail area was still in the dominant position in high speed conditions,it was necessary to aim at that area to start with control of noise source and of the routes of transmission,and one way was to optimize structural parameters of constrained damped rail through simulation analysis of rail vibration and noise;and at the same time,1:1 test bench was to be constructed for damped rails independently designed and developed by China to fully understand noise reduction effect and clarified the applicable scope of noise reduction for damped rails/wheels in high speed railways;the other way was to aim at the noise characteristics of high speed railway to research and develop a composite sound absorption and insulation structure suitable for the sound barrier of high-speed railway to effectively improve the overall noise reduction performance of the barrier.The research result of this paper can provide technical support for the effective control of the radiation noise level of the high-speed EMU and for reducing the enviromnetal noise along the railway.