Prediction Of Interior Noise Of Subway In Tunnel And Optimization Of Sound Insulation Of Subway’s Body

In recent years,in order to accelerate the rapid integration between domestic urban circles,the operating mileage of urban rail transit in China has been increasing.In urban rail transit,the subway occupies an important part.The subway mainly runs in the tunnel.Due to the reverberation of the tunnel,the sound environment in the subway is terrible,which greatly affects the comfort of passengers.Therefore,the prediction of the noise in the subway and the optimization of the sound insulation of the subway’s body can provide some reference and guidance for the low-noise design of the subway in the tunnel.In this thesis,the noise inside the 120 km/h subway in the tunnel was predicted and the corresponding sound insulation optimization scheme was proposed.The main work and conclusions were as follows:Based on the line test,the internal and external noise characteristics of the open line and the tunnel were obtained,and the influence of the tunnel on the internal noise was analyzed.When the subway runs in the tunnel at the speed of 120 km/h,the total value of noise in the subway is around 86 d BA,the main energy is concentrated in the frequency band of 400～1000 Hz,and there is a peak at 800 Hz.Compared with the open line,the total value of interior noise increases by 5～7 d BA.Based on the tunnel reverberation test,the characteristics of tunnel reverberation time were mastered.The reverberation time decreases with the increase of frequency.In the significant frequency band of 500～1000Hz in the subway’s noise,the average reverberation time of the tunnel is 4.3 s.The tunnel model was established,and the sound absorption coefficient of the tunnel boundary was calculated based on a genetic algorithm and reverberation test results.Based on the finite element and boundary element method,the radiation noise of wheel rail was calculated,and the sound source of auxiliary equipment was obtained through the test.The total sound pressure level of the radiated sound power of the wheel-rail is 108 d BA,and the main energy is concentrated in the 1/3 octave band of 400～1600 Hz.The tunnel and subway’s body model were established,and the low-frequency and medium high-frequency sound pressure at the response point of the body surface in the tunnel were calculated by boundary element method and ray tracing method respectively.The effectiveness of the model was verified by comparing it with the experimental values.On this basis,the sound pressure on the body surface in the tunnel was analyzed.The sound pressure of the bottom surface of the body remains between 112～114 d BA,and the bogie area is about 3 d BA higher than the non-bogie area.The sound pressure of the sidewall is maintained between 110～112 d BA,The sound pressure of the roof is around 109 d BA,and the distribution is the same.The prediction model of interior noise was established based on the statistical energy method.The model excitation and parameters obtained from simulation and test were input into the model,and then the interior noise of the subway in the tunnel was predicted.The effectiveness of the model was verified by comparing it with the test values.Through the analysis of the noise contribution in the subway,the transmission path and contribution degree of the noise in the vehicle were obtained,and the weak parts of the sound insulation of the vehicle body were determined.The interior noise mainly comes from air noise.In the transmission path of air sound,the interior noise mainly comes from the door and roof,accounting for 41.3% and 32.3% respectively.Based on FE-SEA,the sound insulation prediction model of roof composite structure was established and compared with the measured value to verify the reliability of the model.On this basis,the influence of material parameters,material thickness,and layout mode on the sound insulation of component composite structure was investigated.According to the survey results,the optimization scheme was selected,and the optimized results were brought into the interior noise prediction model to analyze its noise reduction effect.The weighted sound insulation of the optimized roof combination structure increases by 10.9 d B,and the interior noise decreases by 1.7 d BA,including 1.4 d BA in the peak frequency band of 800 Hz.