A novel mid-frequency formulation for vibro-acoustic predictions. In: RIETER Automotive Conference

Predicting the acoustic behaviour of a vehicle in the mid-frequency range is a challenging task due to the complexity of the involved physical phenomena. Indeed, contrary to the high frequency range, the contribution of the structure-borne noise is of great importance in this range, and in other respect, this frequency field is characterized by high modal densities, which induce huge computational time when trying to solve the problem with usual numerical methods, such as FEM or BEM. Therefore, Rieter Automotive AG, with the university of Florence, is developing a new formulation specifically suited for mid-frequency applications. This formulation is based on a boundary integral equation representation. Randomness is introduced to the description of the geometry of the structure in order to model the increasing sensitivity of the harmonic vibrational responses to any parameter perturbation when the modal density increases. It is shown that the significant unknowns of the formulation are the expectations of the square boundary kinematic unknowns. Indeed, these variables are able to describe accurately the responses of the structures in the low-frequency field and deliver a smooth response in the middle- and high-frequency field, corresponding to the global trend of the structural dynamic response in this frequency domain. The formulation is established for isolated and assembled one-, two- and three-dimensional structures. Numerical applications illustrate the effectiveness of the method.