Other people think he's not paying attention because he's jamming to music, so it's a very affective illusion.
Usually employed by creepers, stalkers, or when a person happens to overhear something about themselves, in which they turn down or off their music to hear what is being said.
Another similar illusion is pretending to sleep. People then open up and start talking about things they may not while one is awake.
"I was earphone phaking the other day, and I heard Amanda likes Joe!"
"Man! I hate Mike! He's such a earphone phaker!"