Efficient Acoustic Trim Components Results Recovery for Industrial Finite Elements Models

In the automotive industry, acoustic trim components are playing an essential role in vehicle Noise, Vibration and Harshness (NVH). They act in three different ways: reducing the structure vibration, absorbing incident acoustic waves and reducing both the structure-borne and air-borne noise transmission. Mastering acoustic trims is key for interior acoustic comfort, a major differentiator in terms of customer appreciation. An elegant and efficient way to solve trimmed vehicle models numerically is the well documented and widely used Reduced Impedance Matrix (RIM) method. It solves the structure and cavity in modal coordinates, while the acoustic trim components are solved in physical coordinates where their complex damping behavior can be fully captured. This method is very accurate to compute structure and cavity results but couldn’t initially recover data such as pressure or displacement inside the acoustic trim parts. Due to its key role in acoustic performance, the inner damping mechanisms, local deformation and other similar information are determinant to improve the understanding of its global influence. This allows to make precise and efficient changes, resulting in vehicle mass and cost reduction. This paper details an additional facultative step to the RIM method which allows to recover trim results with high accuracy, while keeping the same efficient hybrid implementation. Both the theoretical aspects and the implementation sequence in the complete process is discussed. The method is then applied to a trimmed vehicle, evaluating design changes on acoustic trims.