Two-degree-of-freedom active noise control based on internal model control

In this paper, we propose a new two-degree-of-freedom active noise control (2DOF-ANC) system, especially for active road noise control (ARNC) inside automobiles. The feedforward part of the proposed 2DOF-ANC system is a conventional filtered-x LMS (least mean square) adaptive control and the feedback part is based on an Internal Model Control (IMC). The effectiveness of the proposed 2DOF-ANC system is demonstrated through computer simulations using actual car data. System identification of the acoustic field is also discussed. Comparison between the conventional LMS algorithm and the RLS (recursive least squares) algorithm is carried out using experimental data.