The answer to 'dimmer switch buzzing noise' is that a buzzing or humming sound from a dimmer switch is typically caused by an incompatibility between the dimmer and the light bulb. This can happen when the dimmer is not properly matched to the type and wattage of the bulbs being used.
Some common causes include using an incandescent bulb that is not compatible with the dimmer, overloading the dimmer by using bulbs that exceed its maximum wattage rating, or having a faulty or damaged dimmer switch. The buzzing noise can also be caused by electrical interference or a poor connection in the wiring.