Flight test of active structural acoustic noise control system

A flight test is described in which an active structural/acoustic control s ystem reduces turboprop induced interior noise on a Raytheon Aircraft Compa ny 1900D airliner. Control inputs to 21 inertial force actuators were compu ted adaptively using a principal component domain version of the multichann el filtered-x least mean square algorithm to minimize the mean square respo nse of 32 microphones. A tabu search algorithm was employed to optimize pla cement of the force actuators on the aircraft frame. Both single-frequency and multifrequency control results are presented. Noise reductions of up to 15 dB were obtained at the blade passage frequency (BPF) during single-fre quency control tests. Simultaneous noise reductions of 10 dB, 2.5 dB, and 3 .0 dB, at the BPF and next 2 harmonics, were obtained in a multifrequency t est.