Active control of sound transmission through a curved panel into a cylindrical enclosure

Active structural acoustic control of sound transmission through a curved panel into a cylindrical enclosure is investigated. An analytical model of a typical fuselage panel in service conditions is used to design feedback control systems using piezoelectric transducers to reduce sound transmission into the cylindrical enclosure due to turbulent boundary layer excitation.; The investigation begins with the development of a model of a curved panel with attached piezoelectric transducers. The model is validated by comparison to results available in the literature and experimental data. Curvature is shown to increase the effective stiffness of the panel and to affect axial modes more than circumferential modes. The increase in the effective stiffness of the panel increases the structural bandwidth and affects modal order, complicating active structural acoustic control design.; The analytical model is then extended to include static pressure loading resulting from the differential between interior cabin pressure and exterior atmospheric pressure encountered by an aircraft fuselage at cruise altitudes. The model is validated by comparison with results available in the literature. Pressure loading is shown to increase the effective stiffness of the panel, affecting circumferential modes more than axial modes. Furthermore, pressure fluctuations are shown to cause significant variations in panel dynamics, underscoring the importance of the inclusion of pressure loading in the analytical model for accurate prediction of closed-loop control system performance.; The analytical model of the curved panel with attached piezoelectric transducers subjected to static pressure loading is used to simulate a typical fuselage panel in service conditions. To simulate the dynamics of sound transmission, the typical fuselage panel model is coupled to a model of the acoustic field inside a reverberant cylindrical enclosure. The coupling between the structural and acoustic systems is investigated. Results indicate that axial structural modes transmit sound more efficiently into the enclosure than circumferential structural modes.; Finally, a simple, efficient method of including a structural acoustic performance metric, based on the maximum structural acoustic coupling coefficients for each structural mode, in feedback control design is presented, resulting in a simplified model of the coupled structural acoustic system for control system design interations. Feedback control systems for the reduction of noise transmission through the typical aircraft panel into the enclosure are designed for the simplified coupled system using spatial and temporal compensation techniques. The control results indicate that significant reduction of noise transmission can be achieved using the method presented. Furthermore, the optimal control systems designed are shown to achieve performance and to remain stable despite variations in panel position and static pressure loading. A benchmark for active structural acoustic control of sound transmission through a typical fuselage panel into a cylindrical enclosure is established.