EXPERIMENTAL RESULTS OF AN ACTIVE SIDEWALL PANEL WITH VIRTUAL MICROPHONES FOR AIRCRAFT INTERIOR NOISE REDUCTION

Abstract

This work focuses on the reduction of aircraft interior noise by means of actively controlled sidewall panels (smart linings). It was shown in prior work that considerable reductions of interior sound pressure level can be achieved using structural actuators on the lining and microphones distributed in the seat area in front of the linings. Simulation results suggest that the physical microphones in front of the linings can be replaced by so-called virtual microphones. The signals of these virtual microphones are obtained from filtering the normal surface vibrations of the lining through an observer filter. Accelerometers are mounted on the lining structure to obtain the vibration signals. Simulation results of a smart lining with virtual microphones show a mean sound pressure level (SPL) reduction of 10 dB and 5.9 dB(A) in front of the lining. These results must be verified by laboratory experiments applying real-time control because the effects of time variances and imperfect path models will deteriorate the performance of the smart lining. Therefore, the present contribution describes an experimental realization of a smart lining with remote sensors and virtual microphones in a realistic laboratory setup. A double panel system consisting of a primary carbon fiber reinforced plastic (CFRP) structure (fuselage) and a coupled smart lining is installed in the opening of a transmission loss facility. The real-time behavior of the smart lining is tested and the influence of using virtual instead of physical microphones on the SPL reduction is quantified. One focus is on evaluating the robustness of the smart lining under changing environmental conditions.