Method to update the feedback control filter coefficients under active noise control

The active noise control system requires the process of identifying the secondary and the feedback paths previous to updating the coefficients of the noise control filter. These paths, however, are continuously changing in practical systems after the identification. This change inevitably degrades the performance of the system. The authors have already presented a method to update the coefficients of the secondary path filter modeling the former path under active noise control. This paper hence proposes another method to refresh the coefficients of the feedback control filter modeling the latter path. For this refreshment, the method forms two independent equations by using the estimation error involved in the coefficients of the noise control filter. This paper also introduces a system identification technique to solve the equations.