I have heard cases where a ceiling fan has caused a hum, or enhanced a unnoticed hum in a system. The fan which is nothing more than a motor of wire wrapped spinning batteries can create an electric field.

Someone can go months with no problems and as soon as the temperature goes up and the fan goes on a hum is created. Might not even be in the same room but on the same circuit.

I was once playing underneath a fan and the sound bouncing off the blades was weird to say the least.

Fluorescent lights also cause issues.