Analysis The Acoustic Responses Of Vehicle Interior Air Noise Of Acoustic Source

This dissertation using finite element and boundary element method to research the acoustic responses which bring by the vehicle interior air noise.It's a veiy important direction for the research the vehicle acoustic problems.At present, there are still few studies in this area in Chinese. This thesis mainly study the acoustic response of air noise which generated by the EPS in the vehicle development process. On the one hand, studying the basic law of interior acoustic response under air noise excitation; On the other hand, exploring the impact of absorption material on the interior noise, in order to further enrich the content of researching car interior acoustic response.The main research contents as follow:First established vehicle interior acoustic cavity FEM model,then research the acoustic modal of the vehicle interior acoustic cavum by finite element method. Comparing whit the modal analysis of two vehicle interior acoustic cavum FEM model which have seats and without seats,the results show that every phase of modal frequency of the modal which have seats are all below than the modal which without seats, and the modal shape have been changed.lt show that seats are very important for the vehicle interior acoustic cavity modal,and it should not be ignore when establishing the vehicle interior acoustic cavity model.In foundation of the calculate result of the modal analysis,a modal test of the vehicle interior acoustic cavity was been done.and the result of the test prove that the vehicle interior acoustic cavity FEM model can be trusted.For the abnormal noise cases of a certain type of EPS in practical application,can take noise and vibration testing under all conditions when this type of EPS.Finding that when the engine is not running, noise which generated in fast turning the steering wheel is mainly focused in the low-frequency. Then this low-frequency signal resonances under the modal frequency of interior acoustic field, which makes the interior acoustic field in high acoustic pressure level under all modal frequency.Thus, it effects the comfort of driver and passengers.Then the acoustic responses of the vehicle interior acoustic cavity model which has seat are analyzed with noise excitation of invariableness acoustic source and measured EPS separately, and the results in two working states are got. Results show that the response peak frequency is closely connected to the modal frequency of the vehicle interior acoustic cavity. The sound pressure levels of observation points at peak frequency are related to the mode shapes of the vehicle interior acoustic cavity.It is match whit the practice instance that the noise of EPS arouseing some high sound pressure levels noise at some peak frequency will make the passengers fell uncomfortable.In foundation of the acoustics response of the vehicle interior acoustic cavum, this article analysis the influences of the acoustic absorber in places of ceiling, front boarding, floor to the vehicle interior acoustic field. The result indicated that the same material in different positions has different acoustic absorption performance, and even the same material in the same position creates big differences of acoustic absorption performance in different frequency. The simulation result has the important instruction and the reference significance for the control the vehicle internal noise.