| 摘要 |
PROBLEM TO BE SOLVED: To provide a very silent centrifugal fan by minimizing rotation noise. SOLUTION: This centrifugal fan 16 is provided with a first blade line 161B and a second blade line 161C, and the second blade line 161C is arranged while shifted by a half pitch to the first blade line 161B. Because the phase of rotation noises generated by the first blade line 161B is shifted by a half period from that by the second blade line 161C, they are cancelled by each other, so that rotation noises of the fan can be lowered, and consequently, the very silent centrifugal fan can be provided.
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