Stability analysis of the FBANC system having delay error in the estimated secondary path model

The Feedback active noise control (FBANC) scheme is widely used in portable ANC applications. But the FBANC has un-stability problem caused by the modeling error of the electro-acoustic path in its feedback mechanism. To analyze the stability problem, we propose a new stability analysis method utilizing the magnitude component of the open loop frequency response of the FBANC. With the proposed method, a stability bound equation is obtained in terms of the length of delay error of secondary path, the ANC filter length and the center frequency of primary noise. The stability bounds of the proposed method are verified by comparing with both the original Nyquist condition and the simulation results.