Active noise control-from research to reality

This paper traces the development of active noise control (ANC) from its origins in the University Research Laboratories, to its fulfilment in revenue service with airlines. It begins by identifying the need for ANC in terms of quietening the noise from turboprop or turbojet engines, and proceeds to develop the requirements for a viable ANC system. The algorithm used for controlling noise is described, especially its ability to control many independent tones and tones that fluctuate in frequency and amplitude. The system design is described, detailing those features included in the system to make it easy to use, followed by an outline of the hardware used to implement the system. The method of installing, calibrating, and trialling the system is detailed, concluding with the results from a recent set of flight trials.<>