Control strategies for a distributed active acoustic skin

New miniaturization and integration capabilities made available from the emerging MEMS technology allow for the design of artificial linings involving distribution of a large number of elementary cells, that may be composed of loudspeakers and microphones. These smart materials pose the challenge of developing new control strategies to engineer target acoustical impedances, in order to control acoustic fields. This paper investigates the acoustical capabilities of such a distributed active acoustic skin by comparing two control strategies. The first approach is based on local control, where each loudspeaker is current-driven, using a current-pressure transfer function which is designed according to a target acoustic impedance. In the second approach, a distributed control system is implemented such that acoustic waves cannot propagate in a certain direction. Numerical results demonstrate how a well-controlled active skin can substantially modify sound transmission along a waveguide. In this study, each strategy is characterized in terms of efficiency, frequency bandwidth, and robustness. Finally, design parameters for a future prototype are proposed.