Active noise control systems with time varying sound sensor position

The paper summarizes the research on a special class of digital sound processing systems with time varying sound sensor position, conducted in the Institute of Automatic Control, Silesian University of Technology, Gliwice, Poland. These are adaptive active noise control (ANC) systems creating zones of quiet around a microphone, position of which is being changed in enclosure. They use LMS-based adaptive control algorithm, which is parameterized with a model of the so called secondary path. The problem arises when the microphone position is changed during the ANC system operation, because secondary path modeling errors arise. They, in some cases can be coped by the adaptive control algorithm itself, however, in other cases an additional, on-line identification routine has to be used to update secondary path model. These two situations are the subject of the presented research.