The answer to 'why is my junction box buzzing noise' is that a buzzing or humming noise coming from an electrical junction box is often caused by loose or faulty wiring connections. This can happen over time as connections become loose or components wear out. The buzzing sound is typically caused by the vibration of the loose wires or components.
Some common causes of a buzzing junction box include loose wire connections, a bad circuit breaker, a failing transformer, or an issue with the grounding system. It's important to address the problem quickly, as a buzzing junction box can be a fire hazard. If you're not comfortable troubleshooting electrical issues yourself, it's best to call a licensed electrician to inspect and repair the problem.