With this Philips Fidelio NC1 is my first helmet to active noise reduction. Philips documentation explains the system: basically, microphones placed on the headphones identify the ambient noise and the headset sends these sounds that cancel outside noise ... Obviously, the first listen is confusing if you activate the system from the switch to an ear. Besides, it is necessary to charge the battery that powers the ANC function. A micro USB cable is provided. While it is often difficult to describe in words the acoustic qualities of a helmet, it sounds perfectly. Taking into account the fact that it is very isolated from outside me while listening, you really ensures that the sound is meant for very fine music.
Like many high-end headphones rather, that Philips is very comfortable with a hoop that adjusts good and generous cushions which take the form of their owner. Even my glasses frames do not bother me! Another advantage is a cable (with mic for mobile phone) woven material that never tangle.
Finally, of all these qualities, a small criticism: if the headphones can be folded, it comes with a protective carrying case but very rigid and takes up much space.