Feedforward control of sound transmission through a fuselage structure with active trim panels

Abstract

The application of feedback control for the active reduction of stochastic broadband disturbances is widely recognized as superior to feedforward control. However, if the spatial and temporal correlation of sensor signals is high and the control-system configuration is causal, a significant disturbance rejection can be achieved by the application of feedforward control. The reason for this is its ability to reduce both resonant and forced structural vibration. In case of one-dimensional problems, e.g. sound-propagating ducts, the coherence and causality requirements can generally be met and the application of broadband feedforward control is state-of-the-art of science and technology. Yet for higher dimensional problems it can become difficult or even impossible to achieve these requirements. In this research work the attempt was made to exploit the double-wall construction of a typical aircraft fuselage to set up a causal feedforward control system for an active trim panel with improved low-frequency sound transmission loss (< 500 Hz). Different configurations of an active trim panel with structural actuators and sensors have been simulated and experimentally realized in a sound transmission loss facility. Experimental results prove the ability of the investigated smart trim panels to considerably reduce structural vibration and sound power in third-octave bands.