Active control of the flow-induced noise transmitted through a panel

Active control of sound transmitted through an elastic panel when excited by a turbulent boundary layer is investigated. The motivation is the control within an aircraft cabin of the flow-induced noise due to the wall-pressure fluctuations over the fuselage. The excitation is random and so the plate velocity and the radiated sound pressure must be described by spectral densities. These quantities can be obtained from an analysis of the response of the system to a harmonic deterministic excitation and a statistical model for the turbulent boundary layer. Criteria are discussed under which the cross-modal coupling of the structural modes can be neglected when excited by a turbulent boundary layer. When considering subsonic turbulent flows, parametric studies show that each structural mode radiates sound independently. Hence, a suitable strategy for the active structural acoustic control of the sound power transmitted through the panel would be independent feedback control of each structural mode of the system in the low-frequency domain. The performance of this active control strategy is compared to that obtained by controlling the radiation modes of the panel for different numbers of control channels.