Research On A Car Interior Noise In Middle And High Frequency Based On FE-SEA Hybrid And SEA Methods

In these calculation and analysis tools for interior noise, the finite element method and theboundary element method are limited in low frequency range, and then the statistical energyanalysis method is used to analyze the interior noise in high frequency range. For mid-frequencynoise, some scholars points out the finite element-statistical energy analysis method. Based on this,FE-SEA model and SEA model are used separately in this paper to analyze the interior noise inmid-frequency and high frequency. And furthermore, optimization analysis to medium highfrequency noise is carried out by the way of replacing materials and changing the external shape.This paper uses a domestic car as the research model and simulation analysis for themid-frequency noise from100to1000Hz is established using the FE-SEA mixed model. Finiteelement modeling technique is used to these parts of a car such as front longitudinal beam,threshold beam, door beam and A, B and C pillar. Grid is divided in Hypermesh software and forother parts SEA subsystem is adopted to make models. And then based on the finite element nodesthe SEA subsystems of these parts are established in VAone software. For the high frequency noisefrom1000to5000Hz, SEA model is used to carry on analysis. Beam column sections adopt SEAmodeling technique and the same as FE-SEA mixed model the other panel structure parts use SEAsubsystem to make models. In addition, the connection of models, all kinds of parameters, loads andmaterial properties all will be described in detail in this paper.The contribution of aerodynamic noise exceeds other noise and becomes the main noise sourcewhen a car is running at a high speed especially more than100km/h.The wind noise from therearview mirror and the area of the A pillar is regarded as the greatest among the main noise sourcesof car exterior. The airflow experiences a process of separation first and then recombination so thenoise level at the area of side-window is very high. The interior noise increased significantlytransferred by side-window especially in the high frequency range more than1600Hz. Theside-window makes a significant contribution to the power increasing of acoustic cavity of the driver’s head. Toughened glass is used generally in front door of a car now. In order to be able toreduce noise transferring of side-window more effectively this paper deals with the material ofside-window and front windshield. That is, using toughened and interlayer glass and PMMAmaterials to replace the existing glass material and then analyze the impact of the replacement oninterior noise. The weight has been reduced obviously after replacement because PMMA belongs topolymer materials and its density is lower. Meanwhile, the purpose of noise reduction andlightweight has been achieved.Another scheme for interior noise optimization put forward in this paper is to change theexternal shape, that is to say the study of non--smooth surfaces. The research of the influence ofnon--smooth surfaces to interior noise originated in an invention patent of Wangyun etc in ZhejiangUniversity namely-The bionics Non--Smooth Surface Pad Pasting That Has Pneumatic DragReduction Effect. Non-smooth unit is convex closure, pit, Ｌ shape slot or Ｖ shape slot; Thebionics non-smooth surface pad pasting that the invention has pneumatic drag reduction effect isattached on car, passenger train or bullet train surface and automobile body air drag coefficient canbe effectively reduced. Based on this, this paper discussed the application of non--smooth surfacesin the rearview mirror, analyzed its effect on interior noise, make a comparison betweennon--smooth surfaces and smooth surfaces in the rearview mirror in view of their effect on mediumhigh frequency noise in a car. And then two different radiuses of the convex spherical ofnon--smooth surfaces were compared to show their optimization results on medium high frequencynoise.