A principal component feedforward algorithm for active noise control: flight test results

An in-flight evaluation of a principal component algorithm for feedforward active noise control is discussed. Cabin noise at the first three harmonics of the blade passage frequency (103 Hz) of a Raytheon-Beech 1900D twin turboprop aircraft was controlled using 21 pairs of inertial force actuators bolted to the ring frames of the aircraft; 32 microphones provided error feedback inside the aircraft cabin. In a single frequency noise control test, the blade passage frequency was reduced by 15 dB averaged across the microphone array. When controlling the first three harmonics simultaneously, reductions of 11 dB at 103 Hz, 1.5 dB at 206 Hz, and 2.8 dB at 309 Hz were obtained. For single frequency feedforward control problems, the principal component algorithm is shown to be useful for reducing the computational burden and simplifying the implementation of control effort penalties in high channel count control systems. Good agreement was found between the in-flight behavior of the controller and the predicted optimal control solution