Active/Passive Control of Sound Radiation from Panels Using Constrained Layer Damping

Summary A CLD placement methodology based on sound ra- diation was presented. This placement methodology provided an effective rneans of determining optimum CLD locations for selected modes and was experimen- tally confirmed. The hybrid active/passive control results described here illustrate how constrained la.yer damping (CLD) ca.n help a simple feedback controller topology produce reductions in radiated sound power that are close to those of a much more complicated controller topology. The radiated sound power controller that required fif- teen accelerometers whose outputs were processed to compute radiation mode responses, reduced the sound power by 9.2 dB. The results a.lso illustrate that the inipact of the CLD on the closed loop performance de- pends on the CLD’s placement structure atid on the control cost function. The simple controller was able to reduced the radiated sound power by over 8 dB which approaches that obtained by the radiation mode controller. The results demonstrate tliat for this very simple system there is considerable benefit to designing the passive and active characteristics of the controller to- gether. Careful optimization of the CLD placement and controller cost function can be used to implement a low bandwidth, reduced order feedback controller which would be amenable to online adaptation of the controller parameters. Considerable work renmins to be done in order to apply this approach the much more complicated dynaniics of