Vehicle Airborne Noise Analysis Using the Energy Finite Element Method

The Energy Finite Element Analysis (EFEA) has been developed for computing the structural vibration and the interior noise level of complex structural-acoustic systems by solving numerically governing differential equations with energy densities as primary variables. In this paper a complete simulation process for evaluating airborne noise in an automotive vehicle is presented and validated through extensive comparison to test data. The theoretical elements associated with the important paths of the noise transfer from the exterior of the vehicle to the interior acoustic space are discussed. The steps required for developing an EFEA model for a vehicle are presented. The model is developed based on the physical construction of the vehicle system and no test measurements are utilized for adjusting the numerical model. An acoustic noise source is placed at each one of four vehicle locations (engine compartment, front left tire patch, rear left tire patch, and exhaust) where typical exterior noise sources are present in an operating vehicle. The exterior acoustic field is evaluated numerically by the Energy Boundary Element Analysis (EBEA). The acoustic loading from each source is applied on all of the outer parts of the vehicle EFEA model and the interior noise level is computed in the frequency range of 200Hz - 8,000Hz. Predictions for the interior noise level (expressed in a noise reduction format) are compared with test results for all four excitations. The ability of the EFEA method to conduct a panel contribution analysis is used for identifying the panels which contribute the most to the power flow from the structure to the interior acoustic space. Such information is useful in making design decisions when implementing noise mitigation strategies.