Stability improvement for feedback noise control in ducts using a time delay compensator

When applying feedback control in active noise control, phase lag caused by transducer dynamics and time delay between microphones and noise sources limits the bandwidth of the controller considerably. The proposed method to increase stability is to compensate the phase lag by applying a Smith compensator. The compensator needs a model of the acoustic plant. As model, only the transducer dynamics are taken into account in this investigation. The compensator results in a considerable higher control bandwidth. Nevertheless, the demands on the transducer dynamics still remains high. The experiments demonstrate that phase lag can be partly compensated, but the poor transducer dynamics do not allow to close the control loop.