Active noise control in acoustic cavities with flexible walls

A coupled structural-acoustic finite element formulation forms the basis for active control of noise in enclosures bounded by a flexible structure. The primary excitation for the enclosure can be in the form of volume velocity or piston sources as well as excitation acting on the structure. Minimization of acoustic potential energy is employed for deciding the source strength(s) of the secondary sources for active control. The significant feature of this paper is the use of coupled modes for the active control strategy, unlike prior literature. This makes it readily applicable to problems where significant interaction between the structure and acoustic cavity can be expected. Two sample problems are addressed, (a). rectangular enclosure with one flexible wall and (b). flexible cylindrical shell with endplates enclosing an acoustic cavity. The effectiveness of the approach is clearly demonstrated through these examples.