Analogue active noise control

The aim of this article is to present in details all the stages of an analogue active noise control system. As the exemplary plant, an active personal hearing protection device is considered. In the introductory section the plant is presented and the state of the art is reported. In subsequent section, first a way of identification of a continuous-time model of the plant is described and performance limitations are analysed. Then, the procedure for designing optimal controller is proposed. It starts from analysing properties of the plant and choosing a suitable controller structure. Next, coefficients of the controller are found following the design premises. These coefficients serve as initial parameters in the optimisation process. For this process the performance index and appropriate constraints are built. Next, details on implementation of the controller using a chip with switched capacitors are given. Attenuation results of various noises are presented. Finally, cost of the hardware is evaluated. The methodology presented in this article can be considered as a detailed procedure for designing and practically realising cheap and easily tuneable controllers providing good noise attenuation and satisfying several constraints related to frequency band, stability margin, etc.