The answer to 'why is my GFCI outlet buzzing noise' is that a buzzing or humming sound coming from a GFCI (Ground Fault Circuit Interrupter) outlet is usually caused by a ground fault or electrical issue. This is a common problem with GFCI outlets and is often a sign that the GFCI is working as intended to detect a ground fault.
Some common causes of a buzzing GFCI outlet include a wiring issue, a faulty GFCI, or a problem with the connected electrical device. It's important to address the underlying issue to stop the buzzing and ensure the GFCI is functioning properly to protect against electrical shocks. If the buzzing persists or you're unsure of the cause, it's best to have an electrician inspect the outlet and wiring to diagnose and resolve the problem.