Adaptation for active noise control

In active noise control, adaptive approaches play an essential role when dealing with uncertainties and changes in noise and control path dynamics of sound propagation. This article is concerned with two new adaptive schemes. One is a direct adaptive approach which can explicitly update a feedforward controller with guaranteed stability on the assumption that the control path dynamics are known a priori. The other is an indirect adaptive approach which is available when the both noise and control path dynamics are uncertain and changeable. The algorithm consists of online identification of two relevant transfer function models and real-time calculation of the corresponding feedforward controller. The two adaptive schemes are examined in experimental studies in an air duct system and their effectiveness is shown by the results.