I listen to music that I know really really well so that I'm not distracted trying to figure out/remember the lyrics while I study. I also pick one album per class to listen to while I'm really focused studying and listen to it over and over and over again - during an exam I can use hooks from the songs to help me remember the material.
I find that when it's silent I can't read because OH LOOK A SQUIRREL and it takes me twice as long to learn what I'm reading because my mind wanders too much.
There have been some interesting studies that show that we actually aren't capable of monotasking and we make more links when slightly distracted. Like actually seeing the plane parked in the middle of the highway instead of trying to drive through it:
http://blogs.hbr.org/ideacast/2011/1...notasking.html