Abstract: An active equivalent of the λ/4 resonance absorber with a porous plate or foil of flow resistance ρc is described. The porous layer is backed by a loudspeaker driven such that zero sound ...

Abstract: A push-pull electret loudspeaker has been developed which can be used for an active acoustic wall lining.

Abstract: Generalizing the concept of active sound absorption, a system for active impedance control has been developed, so far for plane waves at normal incidence. The active reflector is a loudspeaker ...