Abstract
This paper describes the investigation of an active feedback noise control system in an enclosure surrounded by rigid walls. A higher-order model is required for identification in a rigid-walled sound field because several sound pressure peaks can exit. Since the rigid-walled sound field can be expressed by the superposition of a large number of orthogonal acoustic modes, it is expected that identification can be achieved using a lower-order model for each mode independently based on the modal decomposition technique. Therefore, we propose an active control system with feedback controllers to suppress multiple mode amplitudes independently based on the modal decomposition technique. In the present paper, we verify the characteristics of the proposed system to control four modes numerically and experimentally. The obtained results show that reduction of mode amplitude at each natural frequency can be achieved independently without any mode couplings.
