Vibroacoustic characteristics of a damped box-type structure

In industrial applications, rigid-walled cavities that are enclosed by flexible panels can be commonly encountered. Owing to the coupling of the velocity of the panel with the air pressure in the enclosure, noise and vibration in- and out of- the system is amplified. Such problems are frequently alleviated by passive vibration control, where damping treatments are effective in mid and high frequencies. It has been shown that when such treatments are applied nonproportionally, not only the vibration of the panel, but also the radiated sound pressure from the panel can be reduced, while limiting the mass increase. In this study, the governing relation for this phenomenon is expressed by using the uncoupled modal parameters of the panel and cavity. Complex modes that arise from nonproportionally damped systems are shown to be closely linked to optimal damping characteristics. We further show that the coupling strength between the cavity modes and panel modes are dependent on the spatial distribution of the damping. A damping layer topology optimization problem is formulated to demonstrate the interconnectedness of the modal parameters with optimal damping layer layout.