Numerical and experimental investigation of the effect of structural links on the sound transmission of a lightweight double panel structure

Abstract

This paper examines various models predicting the influence of periodically spaced structural links on sound transmission through lightweight double panel structures. A baseline configuration made up from two aluminum plates connected through aluminum C-section channels and a fiberglass filled cavity has been specifically built and its TL measured for comparison and validation of the investigated models. First, classical decoupled approaches are outlined and adapted for the studied case. Next, a periodic model based on existing formulations is presented. The model allows for a 3D incident field and accounts for the absorption in the cavity with the help of an equivalent fluid model for the fiberglass. Three cases of coupling conditions are considered for the links: a mass–spring–mass approximation, a beam-type approximation and a beam-type approximation where the rigidity and the inertia of the beams are neglected. The measurements show that the bridged configuration strongly reduces the TL at mid and high frequency and exhibits pass/stop bands characteristic of periodic structures. The predictions of decoupled approaches capture the physics of the problem only approximately and with the integration of the mass of the connectors in the context of thin lightweight panels, their agreement with experimental data is further reduced. On the other hand, the results obtained with the periodic model are excellent over most of the studied frequency range. However, in the vicinity of the critical frequency of the thicker panel (around 6 kHz), an overestimation of the TL is observed. This suggests that the model will have to account better for damping and resonant transmission.