ACTIVE SIDEWALL PANELS WITH REMOTE MICROPHONE TECHNIQUE FOR AIRCRAFT INTERIOR NOISE REDUCTION

Abstract

The main issue of this contribution is the reduction of aircraft interior noise by means of actively controlled sidewall panels (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. The use of microphones is undesirable for several reasons and it contradicts the aim of a fully integrated and autonomous lining module (smart lining). Therefore, the present contribution aims at the replacement of the error microphones by a number of structural sensors and an acoustic filter. This method is called the remote microphone technique for active control. Several steps are undertaken to define the smart lining with remote microphones. The whole work is based on experimental data of a double panel system mounted in a sound transmission loss facility. A multi-tonal acoustic excitation, typical for a counter rotation open rotor (CROR) engine, is used as the load case for the definition of the actuators and a broadband acoustic excitation, is used as the load case for the definition of structural sensors. 19 accelerometers are mounted on the lining and 20 microphones are placed in front of it. All sensor signals are sampled simultaneously for deterministic and broadband load cases. The lining is equipped with two inertial mass actuators at fixed positions which are used for the active control. The measurement data is used for the derivation of an observer and for the simulation of a smart lining with remote microphones.