According to one embodiment, a noise reduction system includes a microphone, a loudspeaker, and processing circuitry. The processing circuitry switches an operating mode between a control mode and a path characteristic measurement mode, includes a control filter that generates a control signal that causes the loudspeaker to output a control sound for reducing noise, based on a detection signal obtained by detecting a first sound including the noise with the microphone, measures a path characteristic including an acoustic characteristic between the loudspeaker and the microphone, and generates the control filter by using a measurement result of the path characteristic and a noise feature signal including a feature of the noise.