The Investigation On The Contribution Of Underbody Wind Noise On Vehicle Interior Noise

Wind noise is the most important source of high-speed vehicle interior noise.Meanwhile,with the development of the lightweight vehicle and the noise induced by the side mirrors has been gradually controlled,the wind noise caused by the chassis parts and transmitted through the underbody panel becomes more prominent.The published experimental research shows that the underbody wind noise is mainly contributed in the low-mid frequency band below 500 Hz,and is well know that the low frequency noise has a serious threat to the physical health of the human body.Aiming at this problem,the generation and transmission mechanism of the underbody wind noise was investigated using computational fluid dynamics and computational aeroacoustics numerical simulation method in this paper.The effective measures to reduce underbody wind noise were also explored.The main research work are as bellows:Firstly,the reliability of the simulation calculation method was verified with a simple model.In the exterior sound field,the acoustic directivity characters results revealed that this method could effectively simulate the dipole and quadruple noise source.The results of the interior sound field compared with experiment show that,the error of the spectral curves of the two monitoring points and the total sound pressure level were both within the acceptable range.So that the reliability of the simulation calculation method was firmly verified.Secondly,the underbody wind noise of a real vehicle was analyzed based on the same simulation method.Combined with the modal analysis,the spectral curve at driver's head show that the corresponding frequency of the sound pressure peak was basically consistent with specific natural frequency of the panel and the acoustic cavity.In addition,the influence of different panel thickness on the interior acoustic response was analyzed for lightweight design.After the window noise source contribution was added,the results showed that the noise intensity from the underbody was much higher than the contribution from the windows in the frequency band below 250 Hz,but a reverse result was obtained at the high frequency above 450 Hz.Finally,the effect of damping material on the floor and the airflow separation changing measures of the chassis to reduce the contribution of underbody wind noise was analyzed.The results show that,compared to the butyl rubber damping sheet,the noise reduction effect of the asphalt damping sheet was more significant and the noise reduction is up to 12.2%.In addition,noise level can be reduced by up to 8.06% by adding engine compartment undercover and spoiler.This numerical research on the underbody wind noise of passenger car carried out in this subject has valuable guiding for the further research of underbody wind noise and automobile design and significant reference for the lightweight of the underbody.