Impact of Door Dynamics on Vehicle Interior Low-Frequency Vibro-Acoustics

Interior acoustics represent an essential component of driving comfort in electric vehicles. Numerical simulation is an effective approach for assessing design concepts and enhancing acoustic performance. However, a fully coupled vibro-acoustic model for an entire vehicle remains computationally infeasible. Our approach couples mechanical and acoustic modal models on non-conforming interfaces in the low-frequency range, allowing independent mode combinations. Modal coupling reduces the computational effort significantly from full-order systems with millions of degrees of freedom to a selection of modes of the acoustic and mechanical systems. Modal models of the vehicle structure are derived from measurements with a laser-vibrometer and accelerometers while the interior acoustics are simulated numerically. Since laser-vibrometer measurements are restricted to the vehicle’s exterior surfaces and vibro-acoustic coupling occurs between the inner structural surface and the interior fluid, the structural behavior of the vehicle’s inner surface needs to be determined. We performed modal testing on both the exterior and interior surface of a front door within an entire vehicle due to volume source excitation on the inside of the vehicle. The modal structural behavior of the exterior and interior surfaces for the frequency range of interest already showed an indication of a door dynamic. For a mathematically consistent application of modal coupling method, the eigenvectors of the acoustic and mechanical subsystems must be correctly scaled, i.e. they must be mass-normalized. While the acoustic modes obtained from numerical simulation inherently fulfill this requirement, the mechanical modes extracted from experimental data generally do not. To address this challenge, we investigated a flat plate in numerical simulation and derived a method to determine scaling factors for obtained mode shapes. Proper scaling of the mechanical modes was achieved by applying the scaling method on our measured door modes. The coupled simulation reveals an inherent dynamic behavior of the door.