Active control of sound transmission through a stiffened panel using a hybrid control strategy

This article presents active control laws for sound transmission through a stiffened panel in the low-frequency range. A stiffened panel mounted on a metallic box is used to simulate aircraft fuselage and cabin system. A loudspeaker located outside the box is driven by band-limited white noise to exert acoustic excitation. Dynamic properties of the stiffened panel are characterized through a series of modal testing. Sound isolation performance is evaluated both analytically and experimentally for further efficient control algorithms design. Based on the analysis of these results, a hybrid control strategy combining both feedback and feedforward control is proposed, which utilizes a high-authority/low-authority control architecture. The low-authority control loop is positive position feedback control and high-authority control loop is filtered-X control. When positive position feedback is implemented, active damping is added on the secondary path, which makes filtered-X least mean square more robust, accelerates convergence rates, and reduces residue errors. In the end, the effectiveness of the hybrid control is verified through a serious of closed-loop control experiments. These results demonstrate that sound pressure level could be lowered by a maximum of 15.9 dB at the first resonance frequency. In addition, the overall sound reduction in the cabin is more than 7 dB.