When we first moved into our current house, we would hear a radio station playing through the fireplace. Our fireplace has an iron burner insert with fans. Almost every morning that first Summer we heard a radio playing at the same time, right at 6:00 am to 7:00 am, consistent.
In the winter we had fires in it, so didn't hear it then.
The radio station was not clear. It was muffled so much you could not understand what the DJ was saying and when playing music you couldn't quite make out what it was.
I explored everything. I thought maybe one of our own radios was doing it, maybe left one in the garage with the alarm set for 6:00 am and somehow the sound was coming down the chimney. I asked the surround neighbors, as far as half a mile away (we live in the country) if they had anything going off in their garages or barns at that time, thinking maybe somehow the sound traveled just right and came down our chimney. Nope, no one.
I never did figure it out. Now the fireplace insert does have a motor in it to blow the fan, and I have heard of folks receiving radio stations through their toasters and such, so I thought maybe this was similar to that. I also thought it could have been aliens, even demons and the house was possessed, then I thought maybe angels were singing in the fire place. I mean, when you hear it, it's there! My wife heard it too, we thought of everything.
It went away after about 5 years when we remodeled that room. The walls were completely gutted, I ran additional electric lines for more plugs and installed a big-screen television above the fire place. We've never heard the mystery radio again since we did that work.
Go figure!
We have an in-ground water pump, about 50 feet down in the ground, and it's located about 75 feet from the house. Even though it is that far away, when it turns on, "I" can hear it running through through the pipes in the house, pretty much from any room (and our house is 2800 square foot, all on one floor - kind of split level though.) Still, when the pump turns on, I can hear it anywhere in the house, as it causes a vibration I pick up in the walls, floors, or wherever. My wife doesn't hear it at all.
My guess for the OP is ... he's hearing a vibration through the ground from something that may be miles away. That exact spot is where it's resonating from.
