Active noise cancellation in ducts using internal model based control algorithms

A feedback control algorithm based on the "internal model principle" is proposed to the active noise control (ANC) problem in ducts. Because of its infinite open-loop gain, the controller is able to block noise transmission of selected frequencies at the cancellation speaker position. In other words, the speaker acts like a totally reflective boundary. Stability analysis of the closed loop system is given using the Nyquist criterion. Experimental results agree with the theoretical analysis and show an average of 30 to 40 dB reduction in noise level at target frequencies.<
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