According to one embodiment, a system for reducing interference noise of rotor and stator blades includes rotor blades, stator blades, loudspeakers, one or more reference microphones, and a controller. The rotor blades rotate about a central axis. The loudspeakers are discretely arranged on a circle that has a center positioned on the central axis. Each loudspeaker generates a control sound. The controller causes the loudspeakers to generate control sounds of a same phase and a same amplitude. The control sounds correspond to the loudspeakers. The r is selected based on a preset attenuation level concerning the interference noise, and the k, where a is a length of the rotor blades, b is a radius of the circle, r=a/b, k is an upper limit wavenumber.