Abstract: Experimental investigation on the effect of dual synthetic jet on downstream sound pressure level (SPL) was conducted in a wind tunnel with free stream velocity of Ma=0.4. Dual synthetic jet actuators placed around the trailing edge of the main wing were utilized to control the flow over the flap. Based on the results of pulsating pressure measurement and oil-flow visualization, some conclusions about the control effect on SPL with different flow states were obtained. For an attached flow, the SPL is evidently enhanced by actuation with peak frequency of the initial flow. For a vortex-dominated flow, an appropriate actuation can reduce the SPL and the frequency is an important factor. During a pitching motion, actuation enhances the SPL of the attached flow but does not affect the hysteresis of SPL. While for the vortex-dominated flow, the influence of actuation on SPL is related with angles of attack, and the hysteresis of SPL is weakened. However, the actuation strength has minor impact on the variation of hysteresis. It seems that the optimal actuation for noise reduction has to do with the course of movement.