fans are too much noise

I am using 4 cpu fans in a wardrobe grow and theyre just causing to much noise. They vibrate the wood and i was wondering how I could quiet these fans?

Get some kind of rubber paddin to put in between the fan and case (wherever its mounted too). should help a bit. If u think pc fans r noisy wait till u hear real echaust fans haha

I use that window insulation foam stuff from ur local hardware store. Comes in rolls in various thicknesses. Has sticky sides too.