Ceiling fans are remarkable machines. They are important for regulating room temperatures the majority of the day, every day, for years on end. A noisy fan can quickly become a major nuisance when someone is trying to sleep, or concentrate on work. Luckily, determining why a ceiling fan hums, buzzes or creaks is fairly easy.
Though it may seem like common sense to many, there are no doubt plenty of situations when you might not have all of the blades attached to your fan. Not attaching all of the blades, or an assortment of different fan blades, can cause unevenly distributed weight and inertia, making the fan rock or vibrate.
The glass coverings over any light bulbs attached to your fan may be loose. Often when changing a bulb, these glass fixtures are not properly re-secured onto the fan. If they are loose, over time they can begin to vibrate and hum. This is easily fixed by tightening down these fixtures, and making sure they are properly assembled.
Fans come from the factory with a lifelong lubricant. Noise may be caused by this lubricant settling and coming off of the fan's bearings either through lack of use, or sitting in a box for a long time. Running the fan for 24 hours can allow the fan to automatically work the oil coating back onto the bearings.
Fans that run off dimmer switches often have buzzing or humming problems. This is caused by attaching the switch to a fan which has speed settings that are incompatible with the switch itself. When buying a fan, make sure to get one with three or four speeds and no more. You can bypass the switch by attaching the wires together and using the fan's pull chain to regulate the speed.
Rarely, a defective fan slips through quality control at the factory where it is made. If you have investigated all the other causes and the noise continues, contact the fan's manufacturer, or the store where you bought the fan. In most cases, they will be happy to provide you with a replacement.