Comparison of Feedback and Feedforward Strategies for Active Structural-Acoustic Control of Broadband Sound Transmission into a Cavity

This work presents an experimental comparison of four strategies for active structural- acoustic control (ASAC) aimed at minimizing the transmission of sound through a flat panel into a contiguous cavity. The implemented feedback and feedforward designs, while prevalent in the literature, had not been previously compared on a single panel-cavity system. The test-bed was designed to achieve a dynamic response similar to a single panel in a typical rotorcraft fuselage. This paper presents a performance comparison of four broad categories of ASAC systems such as: classic feedback control (direct velocity feedback DVF), predictive feedback control (generalized predictive control (GPC)), adaptive feed- forward control (filtered-X LMS control) and hybrid feedback-feedforward control (hybrid GPC). The control architectures implemented during this study are all multi-input/multi- output in order to allow the direct application of the resulting insight to more practical situations. Both the vibration and the acoustic performance are recorded for each case under equivalent conditions to allow a fair comparison and are here presented. It turns out that the classic feedback control does not allow to achieve high noise reduction as FXLMS or hybrid GPC that can reduce the averaged total sound power up to 14 dB. In particular the hybrid GPC gives significant improvement with respect to the basic GPC because uses information about the disturbance acting on the system.