The answer to 'why is my GFCI outlet buzzing noise' is that a buzzing or humming sound from a GFCI (ground fault circuit interrupter) outlet is usually caused by an electrical issue. This can be due to a problem with the GFCI itself, loose wiring connections, or interference from nearby electrical devices.
Some common causes of a buzzing GFCI outlet include faulty wiring, a malfunctioning GFCI, or the outlet being overloaded. The buzzing sound may also be caused by a ground fault in the circuit, which trips the GFCI and causes it to make a humming noise. In some cases, the buzzing can be due to electrical interference from other devices plugged into nearby outlets.