Feedback active noise control system with a long secondary path

摘要

A feedback ANC system is disclosed that comprises a microphone (1) and a loudspeaker (2) arranged in a distance from each other; the microphone being acoustically coupled to the loudspeaker via a secondary path (3) and the loudspeaker being electrically coupled to the microphone via an ANC filter (6). The distance between the microphone and the loudspeaker is larger than a value that is determined by the speed of sound divided by 20 times an upper critical frequency of the ANC system.