I am a graduate student and have tried numerous noise canceling headphones to try to block out distractions, however, none of them are fully capable of blocking all sound. What’s worse, they are typically especially poor at blocking out sudden or varying sound, like a sudden laugh from the study carrel across the hall. I have had the greatest success using soft foam earplugs with noise-canceling headphones that are plugged into a device (ipod, computer, etc.) playing beta or gamma waves (many apps and albums to choose from). With this setup, the house could burn down and I wouldn’t notice… just about the only way I can get work done. BTW – if you can’t afford noise-canceling headphones, just get a good-quality over-the-ear pair of regular headphones and make sure you use earplugs with them.