New Analysis of Adaptive Filter Algorithms in Feedback Systems

S.G. Maghrebi, M. Lotfizad (Iran), and M. Ghanbari (UK)


Active noise control (ANC), adaptive active algorithm, feedback system, on-line modeling


This paper employs adaptive filter algorithm for a sort of feedback systems called ANC (Active Noise Control). The applied system consists of an audio system including a microphone, a laud speaker, electrical components and acoustic path. An adaptive filter is installed in the path of feedback; as a result, the common methods fail to analyze how it operates. That is why this article uses "Frequency domain analysis" for the system, based on average and algorithm frequency domain along with causality. With such algorithms as sign-LMS, LMS and FX-LMS in use, the system is stable. The convergence conditions are derived and a bias expression of the weights for the latter problem is presented. The convergence condition and the bias are explicity give for simple examples and their validities are shown by some simulations.

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