I once heard a soccermatch while I was trying to sleep... like it was on the radio or something... only there wasn't any soccer match on at the time (like 1 am). It seemed to originate from a corner in my room where there isn't any radio or anything electronic.
I also heard 2 people talking once, when I was studying in my room... from the same corner... frustrating because I couldn't quite make out what they were saying. Anyway, I figured it was just two people talking outside (my room is on the second floor and near the street) until I looked out my window... nobody there... I could still hear them though... But eventually it stopped.
That was at a weird time in my life though... I was under a lot of stress and having troubles of all kind (being a teenager of 15 years without real friends and having to deal with the ugly breakup of my parents)...
I still have it occasionally though... I think I can hear ppl talk, but then I start to listen and it turns out to just be background noise of a machine or something. I just chalk it all up to fatigue and an overactive imagination.
Plus, the place where I heard the voices before, there's a server (computer running 24/7) now, so all I ever hear comming from there now is the soothing sound of a computer fan.
