| 摘要 |
PURPOSE:To perform excellent noise reduction control by obtaining high coherence between a noise transmitted from an air blower and a reference signal required for active control. CONSTITUTION:A microphone 21 which detects the noise generated by the fan blades of the air blower 20 and supplies it as a reference signal (x) to a controller is provided inside the rotary shaft 31 of an electric motor 30 which drives and rotates the fan blades 23. The rotary shaft 31 is hollow, and a cord shaft 35 is arranged inside it relatively rotatably on the rotary shaft 31 through bearings 36 and 37, and the microphone 21 is fixed to the tip part of the cord shaft 35. The output of the microphone 21 is supplied to the controller through the cord in the cord shaft 35. |
