New efficient and robust narrowband active noise control systems with feedforward secondary-path compensation

In a typical conventional narrowband active noise control (ANC) system, each reference (cosine or sine) wave is filtered by an FIR secondary-path estimate called x-filtering block. The number of x-filtering blocks is twice of the number of targeted frequencies (q), which may pose a bottleneck in system implementation. In this paper, we propose new efficient and robust narrowband ANC systems. An IIR-type feedforward secondary-path compensator is newly introduced in front of the loudspeaker, whose inverse is an FIR minimum phase part of the secondary-path estimate. The remaining FIR nonminimum phase part is used as the x-filtering block whose length may be much shorter. To further reduce the complexity, we use a special bandpass filter bank to decrease the number of x-filtering blocks. As a result, the new systems only require, regardless of q, two (2) x-filtering blocks whose order may be significantly smaller than that of the secondary-path estimate. Modification to the new systems is also made to achieve robustness with respect to the frequency mismatch (FM) between the reference and primary signal frequencies. Extensive simulations reveal that the new systems and their modified versions work almost as well as the conventional system does, and are capable of mitigating the influence of the FM, while enjoy tremendous computational advantage.