A ceiling fan is designed to run for countless hours without any maintenance. The sudden presence of a loud "hum" indicates there is a problem with the fan that must be dealt with immediately. Troubleshoot the ceiling fan to discover why there is a humming noise. You'll need a few common household tools, as well as some supplies from a hardware store or a home and garden shop.
Turn off the electricity to the ceiling fan by removing a fuse or tripping a circuit breaker in the fuse box to disconnect the flow of electricity. Stand a ladder beneath the ceiling fan. Remove the screws on the ceiling cover plate with a Phillips screwdriver. Pull the ceiling cover plate down over the pole attached to the fan so you can see the side that goes up against the ceiling. Place bonding glue on the side of the ceiling cover plate that attaches to the ceiling. Place strips of vibration-isolating material on the ceiling cover plate and hold the strips down until the bonding glue takes hold. This will take a minute or two. Move the ceiling cover plate up the pole and against the ceiling in the position it had formerly occupied. Reattach the screws. Return the flow of electricity to the ceiling fan.
Check whether the ceiling fan can be turned on or off from a dimmer switch on the wall. If so, turn the dimmer switch to its full intensity, as anything less than that will cause the speed control of the fan's motor to emit a "humming" sound. Tape the dimmer switch with masking tape so it can't be adjusted. Replace the dimmer switch with a standard wall switch as soon as possible.
Stand a ladder beneath the fan. Disconnect the flow of electricity that is going to the ceiling fan by removing the appropriate fuse or tripping the appropriate circuit breaker in the fuse box. You can verify that the electricity has been turned off by trying to turn on other lights or appliances that are next to the ceiling fan. Hold one of the blades of the ceiling fan in one hand. Unscrew the plate at the end of the blade from the bracket on the base with a Phillips screwdriver. Cut a piece of vibration-isolating material to the same dimensions as the plate. Apply bonding glue to one side of the vibration-isolating material. Align the material with one side of the plate on the blade. Press down on the material to adhere it to the plate. Release the material after a minute has gone by. Let the bonding glue set for two hours before reattaching the blade to the ceiling fan's bracket. Repeat this procedure with the other blades. Return the power to the ceiling fan when you're done.