PURPOSE: To reduce noise by detecting the number of revolution of a noise source and selecting the reference signal according to the number of revolution, thereby eliminating noise by using always optimum reference signal.

CONSTITUTION: A signal correlative with the noise due to the rotation of the noise source 10 is detected by first sensors 11, 26, and become one side input to a reference signal selector 30, and further, a revolving speed detector 29 detects the revolving speed from an engine rotation signal 10a to input to the reference signal selector 30. The reference signal selector 30 selects the optimum signal among input signals from low-pass filters 13, 28 and the signal is coverted into a digital signal by an A/D converter 14, and inputted to adaptive FIR filters 15, 21. That is, since the first sensors 11, 26 detect the signal correlative with the noise, and the revolving speed detector 29 detects the revolving speed of the noise source, and the reference signal selector 30 selects the reference signal optimum for the revolving speed even when the characteristic of the noise is changed by changing the revolving speed of the noise source 10, the noise is eliminated by selecting the optimum reference signal for every preset revolving speed.