Bose engineers hit the drawing board to come up with their latest model of their popular QuietComfort line of noise-cancelling headphones. The greatest challenge was to move from a "circum-aural" to a "supra-aural" design while maintaining sound quality. This just means that these headphones are smaller than last generation and fit on top of the ear instead of surrounding it. The noise cancelling feature requires a batter power and the QC3s include a battery charger which gives you 20 hours of battery life. They've also improved on the portability of these headphones by making them collapsible and including a carrying case.