The sound went on for about 30 seconds then abruptly stopped.
I was pretty creeped out as I have heard things from my headphones before but assumed it was some sort of hallucination.
After some googling I found out that the input can sometimes pick up radio signals, thus showing my headphones weren't haunted.
Although, about 3 years ago, I remember someone calling for help through my headphones but I can't remember any other details, now that I know it was real, I hope they're okay.
![Sad :(](./images/smilies/icon_e_sad.gif)
I was reminded of this when I heard the Swedish rhapsody in the Sub Universe Fan trailer.