You unlock this door with the key of imagination. Beyond it is another dimension - a dimension of sound, a dimension of sight, a dimension of mind. You're moving into a land of both shadow and substance, of things and ideas. You've just crossed over into the Twilight Zone.
I could not resit
Interesting, i have not experienced anything similar, but, every time when i am in my computer room with my G1 phone, noise comes out of PC speakers when my phone is calling e-mail server, every 5 minutes it happens, it also makes this noise when phone is about to ring , or message arrive.
Electronic signals, radio waves can be picked up by many things , you do not need to have receiver on your PC, probably some sort of interference and maybe frequency of something that matches this transmission that you hear.
I am sure there are people here who know about this stuff here, mine comments are just a guesses, nothing more