[header] How to muffle a fan [title] Check that the fan's blades are evenly spaced and aligned. [step] Bend any blades out of position back into place. Do this very carefully as the blades could snap. 
[title] Oil a fan's motor bearings if you hear a grinding, ticking or rubbing noise as the fan spins. [step] Use a non-detergent motor oil that is lightweight.