Choice magazine tested Noise Canceling Headphones, in their August 2007 edition. Surprisingly the more expensive Bose units did not top the list of those recommended. Top was the Jabra C820s, followed by a discontinued Logitech model and then the Bose QuietComfort 2 and Bose QuietComfort 3.
Some years ago I bought a Panasonic set of Noise Canceling Headphones for using on aircraft. These are very effective for reducing noise, but are uncomfortable on a long flight (such as Sydney to London). These units use active noise reduction, with electronics powered by a AAA battery to create anti-noise. The ear-cups are too small to completely cover my ears. Also the headphones fold into a ball, which is compact, but makes a lump which does not fit in my briefcase. The Jabra and Bose QuietComfort 2 units have larger earcups and fold flat.
Other units are made by companies including: Sennheiser , Philips, IRhythms, Sony, Koss. These include smaller units which designed to sit on the ears and ear buds in the ears, but the larger units which cover the ears completely provide passive, as well as active, noise reduction.
There are also much more expensive units designed for use by the military and pilots, with more sophisticated electronics. In addition there are Electronic Hearing Protection units, designed for protecting against noise which could damage the ears. These units are used by builders and work by blocking sound using passive material and then a microphone to carry sounds at a safe level.