Ok this is a fun exercise. Go here:
www.mp3ornot.com/
and post back whether or not you got the answer correct.
Personally, I got it wrong. Then again, I HAVE been wearing headphones, playing loud guitars, and swinging a hammer for years. The forum that I found this link on had postings from guys who SWEAR they can tell the difference. I think they are full of beans.
www.myspace.com/mortal_engines