Title: A New Modeling Technique of Large Trim Part Air Passages for An Accurate Acoustic Model
text: Finite element models based on the design drawing information are widely applied in the early development stage in the automotive industry. During this stage, the performances of noise and vibration of a vehicle are evaluated by the calculation using FE models. Therefore, it is extremely important to secure the accuracy of the calculation by FE models. Otherwise the problem does not solved with the countermeasures implemented in FE models. To predict sound pressure levels in the passenger compartment, an acoustic model for the compartment must be precisely created. Experimental analysis have shown in the past that narrow air gaps between interior trim parts or between a trim part and a body structure have a high impact on the acoustic transfer functions even in the low frequency range where the issues on booming noise and road noise are often addressed. However, the narrow gaps are usually not modeled in FE models because a lot of small finite elements are needed to express the narrow gaps and much resource is required for the calculation. In this study an acoustic leakage element is proposed to model the narrow air gaps. This element consists of one hexahedral element representing air gaps and several rigid elements connecting adjacent acoustic fields. Specifications for the hexahedral element are experimentally identified by using Helmholtz resonator. The proposed method is verified by the comparisons between the measured and calculated acoustic transfer functions of a vehicle.