Application of Simultaneous Equations Method to ANC System with Non-minimum Phase Secondary Path


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E95-A   No.7   pp.1109-1116
Publication Date: 2012/07/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E95.A.1109
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Noise and Vibration
non-minimum phase,  lattice filter,  cascade connection,  recursive filter,  non-recursive filter,  

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In this paper, we propose a method capable of shortening the distance from a noise detection microphone to a loudspeaker in active noise control system with non-minimum phase secondary path. The distance can be basically shortened by forming the noise control filter, which produces the secondary noise provided by the loudspeaker, with the cascade connection of a non-recursive filter and a recursive filter. The output of the recursive filter, however, diverges even when the secondary path includes only a minimum phase component. In this paper, we prevent the divergence by utilizing MINT (multi-input/output inverse theorem) method increasing the number of secondary paths than that of primary paths. MINT method, however, requires a large scale inverse matrix operation, which increases the processing cost. We hence propose a method reducing the processing cost. Actually, MINT method has only to be applied to the non-minimum phase components of the secondary paths. We hence extract the non-minimum phase components and then apply MINT method only to those. The order of the inverse matrix thereby decreases and the processing cost can be reduced. We finally show a simulation result demonstrating that the proposed method successfully works.