Prediction Of Interior Noise Of Subway Train And Optimization Of Extruded Aluminum Profile For Vibration And Noise Reduction

The interior acoustic environment of subway trains is directly related to the comfort of passengers, and this is one of the key factors to determine its market competitiveness. In this thesis, a SEA model is developed to predict the interior noise of a subway train, and a hybrid FE-SEA model is developed to predict the acoustic performance of the extruded aluminum panels. The models are first validated against measurement and then are used to assess the main sources of interior noise and to optimize the acoustic performance of the extruded aluminum pannels.Firstly, the vibration-acoustic analysis software VA One is employed to develop the SEA model to predict the interior noise of the train running either on the ground surface or in the tunnel. After validation of the model using measured data, it is used to identify the main sources of interior noise and perform acoustic optimization. The results show that, when the subway train run in the tunnel, the interior noise is about 13 dB higher than that when the train runs on the ground surface, due to the fact that exterior noises have no way to escape from the train running in the tunnel. Improvement in trains body panel’s transmission loss, expecially in that of the roof panel, can reduce interior noise. The reduction is more significant when the train runs in the tunnel than when it runs on the ground surface.Secondly, an FE-SEA model is developed to predict the sound transmission loss of extruded aluminum panel. The model is validated using measured data as well as prediction from a BEM model. With this validated FE-SEA model, the influences of vibration and noise reduction materials on the transmission loss is analyzed. The results show that, the vibration and noise reduction materials can influence the transmission loss of the extruded aluminum panel significantly. The air-borne transmission noise reduction efficiency of the panel with damping material sprayed on the surface not receiving noise source is not as effective as that when the damping is placed on the surface receiving the noise source. The latter case is also better than the case in which only the ribs are coated with the damping material. Further, it is shown that, constraint-damping can more significantly improve the sound transmission loss. It is found that the thickness of constraining layer is crucial for the air-borne transmission noise reduction efficiency and energy loss efficiency.At last, the FE-SEA model is employed to predict the sound radiation of extruded aluminum panels with damping treatments described above, and the results are compared with those calculated by the BEM model. Based on these predictions, the influences of vibration and noise reduction materials on the sound radiation can be assessed. It is shown that, the vibration and noise reduction materials can suppress the sound radiation of the extruded aluminum panel significantly. The treatment using a constraint-damping lay perfoms best, that only with the ribs coated with damping material comes the second, and the third is given to the case in which the outer surface is sparyed with damping material.