Bah, real hackers make their own (passive) noise canceling headphones :) Here's mine: http://media.aeminium.org/~slug/2008/headphones/P1010608.JPG

For $18 + headphone speakers, can't beat the price. Worked so well I made two to keep at different locations and also carry one when flying. There's an instructable too http://www.instructables.com/id/Jackhammer-Headphones/

The difference to mine is that I drilled a hole to pass the wires and used hot glue to make sure there's no way sound can come through there.