Abstract: The theoretical calculation and method of shunt loudspeaker controlling duct noise are given in this paper. Firstly, with a disturbance speaker placed at one end of duct as the noise source, another speaker connected shunt circuit is placed at side of the duct as a control unit of duct noise. The duct-loudspeaker coupling model is set up. Secondly, adjustable parameters of shunt circuit are designed to realize independent regulations for the natural frequency and damping coefficient of the control speaker. According to the optimized parameters of shunt circuit, the control speaker can achieve good control effect. Finally, the control effect of the shunt speaker is calculated numerically by using Matlab software. Results show that the designed shunt speaker can control the pressure in the duct effectively. Compared with the conventional active noise control, the major advantage of this method is that the control system does not need error sensor and controller, so the structure is simple and convenient for application.