Active control of transmitted sound power from acoustic enclosure

This paper deals with the active control of transmitted sound power from an acoustic enclosure in which noise sources are installed. With the aim of revealing an effective active control method of the enclosure, a simple model which is cuboid and composed of one elastic panel (upper surface) and five rigid walls is considered by theoretical simulations and experiments. The authors have previously proposed the active control method of transmitted sound power through a panel based on feedforward control which four point force actuators are located on the nodal lines at the frequency which the modal coupling cancellation phenomenon occurs. In this study, this method is applied to the target elastic panel of the enclosure. The simulation results show that the transmitted sound power and the control effect greatly depend on the location of the noise source in the enclosure. In the case that the noise source is located at the asymmetric point with respect to the center of the panel, the control effect may decrease because of the influence of the even-ordered structural modes, which can be excited by the odd-ordered acoustic modes. In order to improve the control effect, the method using both the feedforward control and the direct velocity feedback control is proposed. Finally, experiments were carried out to demonstrate the validity and feasibility of the proposed method.