This guy has the right idea when it comes to how to construct a cheap pair of noise-blocking headphones.
A couple of points, though:
- These are NOT passive noise-canceling headphones, (or noise-canceling headphones of any kind, for that matter). Noise-canceling headphones actual emit sounds 180 degrees out of phase with the noise they are picking up in order to cancel them out. These headphones talked about here dampen all outside noise by muffling any external noise (noise-blocking). Noise-canceling headphones usually let you hear people talking but block out constant drones – these would block out everything (which is not necessarily a bad thing).
- The quality of your headphones you're putting into the ear-protectors will determine how good your music sounds. If you go with a cheap pair of headphones, you probably won't enjoy the end product.
- Not all ear protectors have removable ear-cups like this guy shows – make sure to test the pair you're planning to use before purchasing them.
- Unlike the noise-canceling headphones, this would require NO power to use. However, they can get awful hot if you're covering up your ears with these. The newer noise-canceling headphones try to take this into account and rest on the ears, rather than around the ears.
I've got a pair of Bose QuietComfort II headphones that I've had for about 5 years now. I love them and wouldn't fly without them. However, I could see myself modding a pair of headphones to have these as well for when I didn't want to worry about batteries, or for situations where I didn't want to bring along my expensive Bose headphones (e.g. mowing the lawn, going on a road trip, etc)