Research On The Prediction Model Of High-speed Railway Environment Noise

The prediction model in Chinese Railway Environment Noise Impact Assessment is adopted mainly on the basis of the noise prediction model given by the "Guide Opinions On The Noise Vibration Source Strong Value and The Management Principles Of Railway Construction Project Environmental Impact Assessment"(Documentation No. Railway Plan 2010-44). However, this model was mainly aimed at the wheel/rail noise source’s characteristic in Common-Speed railway. For The high-speed railway, because the differences between the High-Speed Railway’s noise source characteristic and that of the Common-Speed railway is obvious, so, if the original prediction model still continues to be used to predict high-speed railway environment noise effect, a big error will surely be existed, It can hardly meet the need of environmental impact assessment work in China.Based on the analysis of researches on both domestic and foreign railway environment noise standards and prediction models, This article draws out a research suggestion on "The High Speed Railway Environment Noise Emission Standard " for our country, i.e.,30 meters away from the central line of the outboard lateral track of the railway,1.2 meter high above the ground, the equivalent sound level during day time shall not be higher than 70 dB (A), the equivalent sound level at night shall not be higher than 65 dB (A), comparatively to the currently standard used to evaluate common-speed railway noise emissions, the night limit value is 5 dB (A) lower.Based on the field environmental noise research test results of Beijing-Tianjin Inter-city Railway and Beijing-Shanghai High-speed Railway of China, this paper gives out the strong levels of the noise sources of our country’s high-speed train under operation condition; this paper also gives out the main noise source contribution quantity and source frequency characteristic and the acoustic field distribution characteristic; again, this paper defines that Chinese High-Speed railway noise source is mainly composed of the wheel/rail noise at lower part of vehicle, the air dynamic noise at central part of vehicle and electric-current collecting system noise at upper part of vehicle; The equivalent acoustic source model and its source strong level is established in this paper. The wheel/rail noise source and air dynamic noise source can be simplified as thread sound source composed of a long series dipole point sound source, electric-current collecting system noise can be regarded as point sound source of no directivity. According to the acoustic radiation principle, under semi-free field space, buildings complex and eqipped with sound barriers conditions, an acoustic radiation calculation formula is deduced in this paper for different main sound sources; The High-speed Railway’s Environment Noise Prediction Model for environmental impact assessment of China is thus established. Through the practical measurement data, the forecasting accuracy of the prediction model is validated ± 3 dB (A) within range. In this paper, an argument in a proposed high-speed railway construction project is illustrated as an application case example to show that this established environmental noise prediction model is useful and correct in environment noise evaluation, in protective wall application effect and in the reasonable installation of sound barrier. Furthermore, In the light of our country’s high-speed railway noise barriers noise reduction effect limited problem, this paper puts forward the optimization design of sound barrier structure and material suggestion.Research results in this paper provide both theoretical basis and technical basis to predict accurately the high-speed railway environment noise, and to provide optimization design of sound barrier in our country. It has high value of practical application.The innovation of this paper is mainly embodied in the following aspects:Puts forward the high speed railway environment noise emission standard suitable for China’s national conditions; According to the main noise source characteristic of Chinese high speed railway, a high-speed railway environment noise prediction equivalent source model is established. The high-speed railway environment noise prediction model and its calculation parameters suitable for our country is also given; the strong level of each main noise source and its corresponding equivalent position in accordance with the main noise source characteristic of high speed railway in our country is again defined. In Prediction mode, the buildings’ surface sound reflection impact modify value is also added. The innovation contents mentined above can greatly promote the accuracy of high speed railway environment noise prediction in China.