Active noise reduction in ducts of actuating dynamics using two periodic control signals

An actuating subsystem considered as a black-box transfer function in combination with real state space description of an acoustic duct is developed to establish a model for active noise control study. A periodic internal model that can generate 2 periodic signals is further connected to this model to design feedback active noise controllers to attenuate periodic disturbance as well as to improve noise reduction bandwidth. Both results of computer simulation and experiments demonstrate global noise attenuation at a large frequency bandwidth (similar to 71-Hz bandwidth of sound pressure attenuation ratio less than or equal to 0.5) along the duct after the control input location. In addition, the developed controllers can be applied for periodic disturbance of a varying frequency and attain effective noise reduction. Taken together, the proposed design method provides a feasible and applicable way for effective noise attenuation in ducts.