Circuit Hum / Noise
Month ago I noticed a 60 cycle type hum in my bathroom that I associated with the turning on and off of the lights. I replaced the bulbs and the problem still occured but then went away for 6 months.
I noticed a faint humming again last week and this time toggling the lights in the bathroom did not stop the humming like last time. I then switched the breaker off for that circuit and it continued.
Confused, I shut off each breaker in he entire house one by one and found that it would start/stop if I toggled two breakers for other portions of the house (not the bathroom where I hear it; no noise in the portions where those breakers control).
It has since stopped and has not occured again for over a week and i am hesitant to get an electrician here if its not occuring or having to explain this transient, faint 60 cycle type hum.
Is it possible for something outside of my wiring system to cause this hum as I describe? There are no transformers on this circuit either or anything like that.
What could be causing this?