1 New filtered-x recursive least square algorithm for active noise control F. Albu; C. Paleologu Affiliation: Polytechnic University of Bucharest, Romania e-mail: {felix,pale}@comm.pub.ro Abstract A new multichannel filtered-x recursive least square algorithm for active noise control systems is proposed. It is shown that the use of the filtered-x structure, instead of the commonly used modified filtered-x structure lead to a more efficient implementation and similar convergence performance and stability. The paper is also focused on examining the benefits of auxiliary normal equations solving methods needed by the formulation of the RLS problem. The behavior of the proposed algorithm is investigated in cases of ideal and non- ideal acoustic plants. Keywords: filtered-x structures, active noise control, recursive least squares 1 Introduction During last years many adaptive algorithms have been proposed for multichannel active noise control (ANC) applications. In ANC systems, an adaptive controller is used to optimally cancel unwanted acoustic noise [1], [2]. Primary field d Adaptive filter w Plant h Plant model ˆ h  + + Reference signals x Algorithm Actuator signals y v Error sensor signals e I K K K Fig. 1. Block diagram of the filtered-x structure for active noise control.