Harman Kardon NC Premium Over-Ear Noise Cancelling Headphones - Wired Proprietary closed-loop, active digital noise-cancellation technology analyzes and optimizes the audio signal before it reaches the listener's ears for the most accurate noise cancellation possible Optimized driver system for sonic clarity and accuracy even at low volume levels Passive playback using the supplied bypass cable means you can enjoy continuous playback (minus the active digital noise-cancelling) even when the battery is dead USB recharging eliminates the need for batteries or an extra charger Sandblasted steel and black matte housings deliver sophisticated, modern design