When you're listening to your favorite tracks you don't want to hear the rattle of the train, one side of a mobile phone conversation or the drone of airplane engines. Rather than cranking up the volume and endangering your hearing, invest in headphones designed to cut out the background noise. There are two approaches; in-ear buds that fit so well into your ears that extraneous sound can't get in, and active noise cancellation that generates white noise to disguise the racket - some systems actually sample the ambient sound and tune the white noise to remove it more efficiently.
Creative offers one of each style: the tiny, sleek, in-ear Aurvana; and the bulkier, cushioned HN-700s (although these do fold up neatly to pack away). Both are far cheaper than most equivalent headphones. So do you get budget features too, or will they bring you to audio nirvana?