251 遠心送風機における翼通過周波数騒音の低減化(G05-4 流体騒音,G05 流体工学)  [in Japanese] 251 Reduction of Blade-Passing Frequency Noise in a Centrifugal Blower  [in Japanese]

Active cancellation of the BPF noise radiated from a centrifugal blower is conducted using vibrating flat plates driven by piezo-electric actuators. The fundamental BPF noise can be reduced effectively by controlling the effective noise source extent which is obtained by correlation analysis between the data of pressure fluctuation on the scroll surface and radiated blower noise. Research attention is focused on the effect of blower rotational speed, distribution pattern of the effective noise source is determined precisely. The extent of the 1st BPF noise source can be restricted in the vicinity of the cut off apex, while that of the 2nd BPF moves irregularly together with the blower operating conditions.