Ok. In Australia breakers are always (to my knowledge) broken up into lights vs power points/fixed electrical. Definitely "geographical" after that though of course. Usually light circuits aren't RCD protected so are on separate circuits.

Still might be worth turning all off bar the one you think it is. Might help rule out something elsewhere somehow transferring the sound? If you know which breaker you could at least go around the house and see what's still active.

Edit: Yeah Tony said the same - missed it.