| 摘要 |
PROBLEM TO BE SOLVED: To diminish or remove a whizzing sound of a specific frequency, by arranging a plurality of vanes of a cooling fan unequally and performing their fitting, and making their whizzing sounds have a plurality of kinds of frequencies. SOLUTION: A radial fan 1 is composed of a disk 2, and a plurality of plate vanes 3 fitted vertically to one surface of this disk 2. Here, the positions of individual vanes 3 of the radial fan 1 are arranged unequally. And unbalance of the radial fan 1 is corrected by attaching a compound etc., properly. Consequently, whizzing sounds of a specific frequency can be diminished or removed, by scattering the frequency components of whizzing sounds of the radial fan 1 into a plurality of frequencies, when it rotates at a high speed just like that of a power tool.
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