Design and Implementation of an Active Absorber

Abstract

Active control may be introduced to resonators to improve noise control performance. Many active controllers depend on accurate transfer functions from speakers to error sensors to generate destructive interference. These transfer functions are sensitive to acoustical parameters in noise fields where error sensors are installed. An alternative strategy is to modify internal resonator impedance instead of destructive interference in noise fields. This approach focuses on the internal dynamics of a resonator and uses an equivalent primary source to model the external noise field. A controller is designed on the basis of the internal dynamics and is hence independent of external acoustical parameters. The controller improves absorption by minimising noise reflection inside the resonator. Such an active absorber is implemented and tested in experiments to achieve near perfect absorption performance in a wide frequency range. The closed-loop system is stable and reliable with respect to significant variations of acoustical parameters in the external field.