First take the radio somewhere else & be sure its OK.
Then start throwing breakers one at a time. Use a transistor radio as a
noise detector. After you throw the main breaker use the radio to sniff out
the noise. It can still be in your house if its something battery op.
Take a walk around the area to pinpoint it. It can be quite far away.
At the shop we had an int buzz you could even see on a TV. The electric co made many trips & finally found something breaking down 1/2 mile
away.
73 Zeno
LFOD !