This paper presents a frequency domain simultaneous equations method that can automatically recover the noise reduction effect degraded by secondary path change. Another time domain simultaneous equations method has been proposed in ACTIVE99. Differently from the filtered-x algorithm, these simultaneous equations methods do not require the secondary path filter for estimating the coefficients of noise control filter, instead, exploit the estimation errors involved in the coefficients. In practical systems, the coefficients of noise control filter are estimated with different errors per sample time. The simultaneous equations methods exploit the different estimation errors; thereby yield two independent equations giving the primary and the secondary paths as unknowns. By solving these two independent equations, the simultaneous equations methods directly estimate the noise control filter coefficients minimizing the error sensor output. The frequency domain simultaneous equations method can estimate the noise control filter coefficients without using the additional filter and the system identification circuit that are necessary for the time domain method. This paper presents a simulation result to examine that the proposed method autonomously recovers the noise reduction effect after paths changes.
展开▼
