Ceiling fan troubleshooting when noise is the problem can be a challenge.
Do you have a different problem? See 'Electrical Repair' for a complete listing of all electrical topics.
Motor noise is a big complaint. Over time the windings on the motor may deteriorate. The motor will hum louder as a result. Not a lot you can do about this, short of replacing the fan.
You should not use a dimmer switch for a fan. Incorrect power will cause the motor to hum and possibly ruin it. Only use speed controls that are compatible with the fan you have. See the owners manual to find out what to use.
Vibration is also an issue. Even when the fan is properly balanced it still vibrates. The better quality the fan the more vibration isolation it likely has. Is it a cheaper older fan? You might be able to add a rubber gasket at the base plate. Again, there may not be a lot you can do for normal vibration.
Is something rattling inside the fan? Take the housing apart and check for loose parts or screws. Tighten anything that is loose. Make sure all the wires are tucked into the proper locations.