Have you ever had the experience of being somewhere away from the noise and din of the city, perhaps in the mountains somewhere, or in a desert; and as you sat and looked at the starry sky, you were amazed at the silence?  It was quiet, right?  Wrong!  It wasn't quiet; it was just that you couldn't hear the sounds.  Strange but true is the fact that the atmosphere around you is filled with a thousand voices, but you just aren't tuned to them.  You can't pick them up.  If someone asks you what kind of a device you're listening to, you would say, "Well...it's a radio."  Or "I'm listening online over the internet."   There are "voices"—sound waves, cellular and digital signals all around us!