A novel narrowband active noise control system with significantly reduced computational cost

In conventional narrowband ANC systems, each reference cosine or sine wave has to be filtered by an estimate of the secondary-path. This filtering element is called x-filtering block. The number of x-filtering blocks is proportional to q where q is the number of targeted frequencies. When q and/or order (Mcirc) of estimated FIR-type secondary-path are not small, the computational cost due to the x-filtering blocks may become a bottleneck in real system implementation. Here, we propose a new narrowband ANC system structure which requires only two (2) x-filtering blocks regardless of q. All the cosine waves (or sine waves) are combined as an input to a x-filtering block. The output of this block is decomposed by an efficient band-pass filter bank into filtered-x cosine or sine waves for the filtered-x LMS (FXLMS) algorithm that follows. This way, the computational cost can be significantly reduced. Extensive simulations reveal that the new system indicates performance similar to that of the conventional system, but enjoys great advantages in system implementation.