I have that kind of thing a lot too. Talking, music, radio/tv stuff mostly. It never really freaks me out, though sometimes it is pretty disconcerting and I'll go looking for the (non-existent) source. Haha. One time psych asked me, "If you know they're not real, why do you go looking for them?" Uhhhhhh, dunno! (It's 'just to be sure', but the question remains.) She says do not worry. They're not talking to me or telling me to do anything. The first time I inquired about it, she asked if there had been a fan or something running. There was, and that sort of thing is very common "source" (though not necessary). Generators really bring it on strongly for me and I used to work next to one. Hours and hours of "conversation" happening behind my back was quite annoying. My theory is that it's our brains trying to make sense out of random sounds.