The Active Control of Sound in Aircraft

Active Sound Control is an effective means of reducing low frequency sound in the cabins of passenger aircraft. This paper reviews and provides some guidelines on the issues of implementing an active sound control system in an aircraft cabin. I start by explaining the principles of active sound control, the advantages of its application to aircraft cabins and the expected sound reduction. There are two important implementational aspects of an effective system; it must match both the acoustics of the cabin sound field and track the changes in the unwanted sound. The acoustic matching is achieved by careful design and location of the loudspeakers. These have to be both lightweight and efficient at low frequencies and also must fit acceptably into the aircraft trim. To track the changing sound requires a powerful digital controller designed for the aircraft environment and a sophisticated control algorithm.