Liu Y., Hung C.

In most practical applications of active noise control, the acoustic feedback is a major problem that often interferes with the operation of the control system and even renders it unstable. The traditional dual-microphone reference sensing technique is discussed and modified in this paper. Further, we propose a frequency-domain method based on transfer function to reduce the influence of acoustic feedback based on plane wave transmission theory of sound in a duct. The original signal of primary noise is obtained from the measured signals of reference microphone and error microphone which are transformed to frequency domain by FFT and operated by the proposed method. Finally, the performance of the proposed method is verified by means of an ANC experiment in a finite-length duct. The results showed that the proposed method can effectively reduce the influence of acoustic feedback. In practical application of active noise control in a duct, the adaptive control or other control method incorporate the proposed method in this paper will improve the stability and performance effectively