Hybrid active/passive control of sound radiation from panels with constrained layer damping and model predictive feedback control

Feedback control of aircraft sidewall panels has been studied for reducing interior noise due to turbulent boundary layer excitation of the fuselage. Online adaptation of the feedback controller parameters can be used to track pressure, temperature, and structural variations, but the associated computational burden can be overwhelming. This work describes a hybrid active/passive control approach, where the passive components reduce the complexity of the active system. Constrained layer damping provides damping at high frequencies, and a generalized predictive controller is used at low frequencies. Experiments were conducted on a panel subjected to broadband speaker excitation in a transmission loss facility. A piezoelectric actuator provided control input to the panel, accelerometers provided error feedback. Two sensing configurations were studied: one used full-state feedback to control radiated sound power, estimated from 15 accelerometers on the panel; the other used dynamic output feedback to control the summed responses of 4 accelerometers. Active noise reduction from different locations of constrained layer damping is discussed. The addition of the constrained layer damping makes it possible to achieve good noise reduction with the simpler 4-accelerometer sensing configuration.