The 2009 International Symposium on Active Control of Sound and Vibration
In this paper a velocity feedback system for the reduction of sound radiated by a simplified aircraft double panel is analysed experimentally. The double panel rig consists of a thin aluminium panel and a honeycomb trim panel, coupled acoustically by the air cavity between them and structurally by four elastic mounts. Nine small-scale electromagnetic actuators are mounted in the cavity such that they can react against the two panels. A pair of velocity sensors is added at the two actuator-panel junction points. The two velocity signals are first asymmetrically weighted and then subtracted to form the error signal. Finally, the error signal is fed back to the actuator via a constant amplification gain. In this way the control loops produce a combination of relative and sky-hook active damping, which tends to reduce the response and sound radiation of the double panel at low resonance frequencies. The stability and performance of the control system are analyzed experimentally as a function of the weighting factor. Reductions between 10 and 25 dB in the radiated sound power have been measured at low frequency resonances of the double panel.