An amplitude constrained FxLMS algorithm for narrow-band active noise control applications

Annoying noises generated by industrial equipment (such as engines, transformers, fans, etc.) might persist in some environment, resulting in a comfort decrease for people present in that area. Active noise control solutions could improve environment sound quality significantly, especially at low frequencies where standard passive solutions would be much bulky and expensive. Narrow-band approaches have been widely discussed in the past because of their simplicity and effectiveness in the cancellation of tonal noises. In this paper the authors propose a novel adaptive algorithm based on narrow-band Filtered-x Least Mean Square algorithm which, instead of adapting two taps per tone simultaneously, updates only one tap at a time and derives the other one from the knowledge of the adapted tap and the a-priori known amplitude of the disturbing tone. Proposed solution implicitly prevents instability conditions of standard two-taps solutions, avoiding consequent high comfort deterioration and hardware breakups. Experimental simulations have been carried out to show proposed algorithm behaviors under stress conditions, proving that its performances are comparable with those of classic narrow-band algorithm.