Prediction And Measurement Analysis Of Noise Inside And Outside Metro Train

As a public transportation,the subway has become an effective way to alleviate traffic congestion due to its convenience,speed,energy saving,high safety,and large transportation volume.In recent years,it has developed rapidly in the first and secondtier cities and has gradually become a major backbone of public transportation in cities.With the development of subway in our country,the problem of train noise has become one of the urgent problems to be solved.The noise in the train directly affects the comfort of drivers and passengers,and becomes an important indicator to measure the quality of metro,The noise outside the train has caused great troubles to the production and life of residents along the route.This paper uses numerical simulation and measurement methods to study the noise problems inside and outside the train.The main research contents are as follows:(1)Combining the advantages of the FE method,the hybrid FE-SEA method,and the statistical energy method,a full-band interior noise prediction and model was established,and the test results were extracted and compared to verify the reliability of the model.At the same time,compared with the calculation time and the total number of units of the existing commonly used methods,this method has greatly shortened the time and improves the efficiency under the premise of ensuring the calculation accuracy.(2)The A-weighted noise level at each standard point shows a trend of rising first and then falling.There is an obvious peak at 630 Hz,which is consistent with the peak of wheel/rail noise,indicating that wheel/rail noise is the main source of interior noise,and the noise energy is mainly concentrated in the 200～1600Hz frequency band.(3)The main frequency band of structure noise is 20～200Hz,and the main frequency band of airborne noise is 200～5000Hz,of which 500～5000Hz frequency band is the most significant.Wheel/rail noise should be paid full attention to as acoustic excitation in the prediction of train noise.(4)Through the actual measurement and analysis of the interior noise,it is concluded that when the speed of train is from 75km/h to 115km/h,the noise is increased by 5.24 d B(A).The noise in the driver’s room is 2～5d B(A)lower than that in the passenger room.The noise above the frame is 0.4～1.7d B(A)higher than the middle part of the train.The noise characteristic has the same trend.The dominant frequency band is mainly concentrated in the 400～1600Hz.The noise has an obvious peak at the center frequency of 630 Hz,and the maximum sound pressure level has increased by about 11 d B(A).(5)When the speed is 70km/h,compared with the steel spring floating slab track(FST),the total sound pressure level(SPL)under the regular slab track increases by 1.64 d B(A),the ladder-type sleeper track decreases by 0.95 d B(A).When the speed is90km/h,compared with the FST,the total SPL under the regular slab track increases by2.99 d B(A),and the total SPL under the ladder-type sleeper track decreases by1.02 d B(A).Ladder-type sleeper track and FST have higher A-weighted SPL amplitudes at 20Hz～100Hz and 1600 Hz than the regular slab track,and lower amplitudes at400～1000Hz than regular slab track.(6)The total SPL in the tunnel is about 11 d B(A)higher than that of the birdge.The significant frequency band of the noise inside the tunnel and the bridge is 400～2000Hz,and there is a significant difference in the interior noise within 20～5000Hz.The noise difference in the train is the largest at 2500 Hz,which can reach 17.58 d B(A).(7)The statistical energy analysis model of train was established.The result shows that: when the train speed is 60km/h,the sound radiation energy outside the train is mainly at 400～1600Hz,and the maximum value appears at 800 Hz,and the variation of wheel/rail noise is basically the same.The contribution of noise outside the train from large to small is wheel/rail noise,window,side wall,door,bottom plate,roof and end wall.The vehicle body vibration radiation noise contributes a lot in the low frequency range.within the center frequency of 20～100Hz,The main sources are windows and side walls;within the center frequency of 100～500Hz,the contribution of wheel and rail noise is greater than that of the vehicle body,but the difference is small;within the center frequency of 500～5000Hz,the contribution of each segment of the train shows a downward trend with increasing frequency,the contribution of wheel/rail noise gradually increases.(8)After the rail is installed with damping,the environmental noise on both sides of the line during the three main periods will be significantly reduced.The installation of damping plates on the rail has a significant effect on reducing the noise outside the train.In the frequency of 20～80Hz,the SPL before and after the installation of the damping plate is not obvious;In the frequency of 80-5000 Hz,the SPL after the installation of the damping plate is significantly reduced.Comparing the initial state and the rail damping,it is found that the reduction amplitude of the passing noise level at 7.5m outside the train is between 2.1-3.8d B(A),and the reduction amplitude of the passing noise level at 30 m is 1.9-3.2 dB(A).