Experiment And Simulation Analysis Of Noise Reduction Performance Of Vehicle Porous Materials

People are paying more and more attention to the noise problems of the car,because it seriously endangers the user's physical and mental health.Researchers use a series of control methods to reduce cab noise,to protect the user's physical and mental health and enhance the comfort of the car.Studies have shown that a broad and effective way to control vehicle noise is to reduce or eliminate noise during the propagation of noise.Among them,laying the porous material in the inner wall of the body structure is a simple and effective measure.Melamine foam is a typical porous materials,its structure contains a large number of interconnected pores,which is conducive to the absorption of sound waves.The body structure of the car is often different and the source of noise is more complex.So the choice of single-layer cylindrical shell structure as a research object to reduce the impact of these two cases.Based on the experiment of typical cylindrical shell structure noise reduction,it is concluded that melamine foam is not effective for suppressing structural vibration,which means that it can't weaken radiation noise better.But in the 160?1000Hz band,melamine foam noise reduction effect is obvious.By analyzing the sound insulation at different points in the cylindrical cavity,the effect of noise reduction of melamine foam is obvious and the error range is ±3dB.The acoustic finite element model was established according to the noise reduction experimental structure and the sound field environment.Based on this model,the acoustic mode is analyzed and compared with the experimental method and the analytical method.The error is in the range of 0.78?5.06%,which verifies the noise reduction experiment simulation modeling is more accurate.Based on the finite element model of cylindrical shell noise reduction experiment,the influence of pore acoustic parameters and density on the noise reduction performance of melamine foam was studied.The results show that the effect of changing the porosity,flow resistance,zigzag factor and viscous characteristic length of melamine foam on its noise reduction performance is significant.Automotive noise is mainly concentrated in the 250?500Hz band.For reducing the noise in this band,the porosity of the melamine foam is about 99%.for the suppression of noise in the range of 400-500 Hz,the flow resistance is more suitable in the range of 12000?30000Pa·s/m~2;for reducing the noise in the 250?400Hz band,the flow resistance is better when the flow resistance is in the range of 50000?80000Pa·s/m~2.When the twist factor is in the range of 1.5?1.9,the noise reduction performance of the material is better.The material with a density of approximately 9kg/m~3 can better suppress the noise in this band.The size of the channel between the pores is 0.06 mm can play a better suppression effect;While the change in pore size has little effect on the noise reduction performance of the material.