| 摘要 |
PROBLEM TO BE SOLVED: To provide a low noise fan capable of eliminating inconvenience wherein a sound absorbing mechanism is conventionally arranged for reducing noises generated by an air sound and the large execution work area is required which, increases a cost, and increases a pressure loss of an air flow for reducing a predominant periodic sound characteristic of the fan. SOLUTION: In this low noise fan, an acousting softward boundary generated by a rotating speed of the fan and a specific frequency by the number when a blade of the fan passes through a nonuniform place of the pressure distribution and the speed distribution, offset by a periodic sound corresponding to the predominant periodic sound from a secondary sound source arranged in the vicinity of a predominant period sound sound source before diffusion, and reducing a sound pressure level of the predominant periodic sound, is opened in the predominant period sound sound source. Thus, the predominant periodic sound can be reduced in the acoustic software boundary for largely reducing a physical quantity more than a conventional sound absorbing mechanism, the execution work area for reducing the sound can be extremely reduced, the pressure loss of the air flow is almost eliminated, a construction cost and a running cost of a plant and a wind tunnel can be reduced, and performance can be improved.
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