Research On Characteristics And Distribution Law Of Noise Field In Underground Subway Station Platform

The underground station of the subway line is the main form of the subway station.The noise generated during the entering and leaving process of the subway train has a great influence on the platform space of the station.Therefore,it is very necessary to study the noise field distribution law of subway station platform and analyze the appropriate noise reduction measures for the wheel-rail noise characteristics of subway trains.This is of great significance for improving the acoustic environment of underground subway station platform.Based on the Beijing Natural Science Foundation Project(8172040),this paper uses the field measurement and simulation methods to carry out the following research:(1)Firstly obtain accurate information on the wheel-rail noise characteristics of subway trains entering and leaving the station.This paper selects Beijing Subway Line 2 Xizhimen Station,Line 6 Ping'anli Station,Line 6 Chegongzhuang Station,Line 1 Gucheng Station,Line 1 Apple Orchard Station to conduct noise signal collection and testing.The spectral characteristics,peak frequency and sound pressure level range of the sound source are determined,and the traffic noise index,noise pollution level and acoustic exposure level are calculated and analyzed.(2)According to the noise characteristics of the subway trains obtained by the test,the fluid-solid coupling simulation model of the air cavity of the subway station is established by ANSYS finite element software.The calculation frequency is based on the one-third octave and test data.5 kinds of frequencies:63.5Hz,80Hz,100Hz,125Hz,160Hz,in which the noise peak frequency is 80?125Hz.The calculation results are compared with the test results to verify the reliability and rationality of the modeling method.(3)The model simulation clarifies the distribution law of the noise level of the platform layer when the platform form,the number of sound sources,the height of the platform door,the wall sound absorbing material and the sound absorption coefficient of the platform door change,and the noise sound pressure at different height levels on the platform layer,and thus determine effective noise reduction measures,provide a basis for improving the acoustic environment of the platform.Through the actual measurement and simulation calculation in the study,the following conclusions are drawn:The noise outside the subway train is mainly low-frequency noise during the process of entering and leaving the subway platform.The main frequency band of the noise is below 200Hz,and the peak frequency is 80?125Hz.When other conditions are the same,the noise level of the island platform is relatively lower.The distribution of the sound field cloud map of the circular section platform has a certain similarity and extension of the figure compared with the rectangular section platform;when the subway train passing by both sides at the same time,the noise sound pressure level of the passenger waiting area of the platform will increase by 1?5dB compared with the case where there is one train passing by one side;the installation of the platform door will have a significant shielding effect on the wheel-rail noise propagating to the passenger waiting area,and the noise reduction effect of the high platform door is better than that of the low platform door.setting the low platform door for the noise reduction of the wheel-rail noise up to 1?11 dB,and setting the high platform door for the noise reduction of the wheel-rail noise up to 2-20 dB;the sound pressure level curves at different heights of the platform doors from the ground 1.5m and 1.8m horizontal lines have certain similarities in the trend.There are certain shifts and peak changes between the curves,and the numerical differences is related to the form of platform doors.Changing the wall sound absorbing material can effectively reduce the noise level.When the sound absorption coefficient increases,the noise reduction effect gradually increases;but when the sound absorption coefficient increases to a certain extent,the reduction of the sound pressure level tends to be gentle,or even to fall back;there is a relative optimal maximum of the wall sound absorption coefficient at each frequency.In the selection of sound absorbing materials,it is necessary to comprehensively consider the sound absorption effect of different frequency bands and the effective economic sound absorption coefficient range;whether it is a high platform door or a low platform door,the change of the sound absorption coefficient of the platform door is not obvious for the noise reduction effect of the noise field.the sound absorption coefficient is increased by 0.1,and the noise reduction effect is not higher than 3dB.Therefore,this measure has little effect on the noise reduction of the passenger waiting area.It is not recommended to reduce the noise by changing the sound absorption coefficient of the platform door.Figure 91,table 10,reference 85.