I have a set of JVC (HA-NC100) headphones which have been tested to capacity as a passenger on military aircraft (C-130), and found to be excellent.
They are a little bulky, being 'over the ear' type, but fold neatly into a 5" x 5" soft bag for travel.
They will cancel about 80% (estimated) of jet engine noise, airconditioners, industrial machinery and similar, but are not particularly effective on sudden or erratic noise sources.
They seem to work best with a constant input of ambient sound, like aircraft engine noise.
Runs on a single AAA battery for about 24 hours use, cost around $US100, come with aircraft twin point adaptor plugs, and a standard iPod/walkman type plug as well. Music sound quality is excellent from the speakers.
Highly recommended for airline or train travellers, might not work for snorer's partners too well.
