As an effort to reduce energy consumption and hazardous emissions, lightweight design has become more and more important for new vehicle developments. Substituting conventional steel material with other low-density materials in building vehicle structures is one typical approach for lightweight designs. To investigate the influence of the structural weight change on the noise, vibration and harshness (NVH) performance, this study presents a structural-acoustic coupled model of a rectangular shaped cavity enclosed by 1 or 2 flexible panels. Using this modal, parametric studies aiming at reducing the total structural weight and simultaneously improving the NVH performance are conducted. For the case of a single flexible panel subject to a point force excitation, it is found that substituting the heavier steel panel with a lighter Al panel may actually reduce the sound radiation inside the cavity at the low frequency range. On the other hand, at higher frequencies, the noise radiation level is roughly inversely proportional to the material density. For the case with dual flexible panels, although it is predicted that the two panels are weakly coupled through the acoustic cavity at most frequencies, the noise level may still be reduced at a lighter structural weight in certain cases.Copyright © 2012 by ASME