[. . . ] At work, at home, in public transport, on `plane, train or bus journeys - noise is with us wherever we go. [. . . ] The first , , open-air" stereo headphone with NoiseGardTM active noise compensation At just 110 g, this , , open-air" stereo headphone with active noise compensation is extremely light and provides excellent wearer comfort. When you are wearing the NoiseGardTM HDC 451 you will still be able to join in conversation - the voice of the person talking to you is scarcely changed, since the speech frequency is practically unaffected by compensation. Understanding speech is even improved by NoiseGardTM, as , , upward-masking" by low-frequency sound is eliminated. switching ON/OFF ON/OFF switch for the power supply to the compensation electronics is situated on the battery box. If the power supply is switched off or the batteries are worn out, the headphone can still be used as a normal headphone without noise compensation. So, now you can enjoy your music undisturbed, without having to turn the volume up so high that surrounding noise is completely drowned out. [. . . ] KG declare that this device is in compliance with the applicable CE standards and regulations. [. . . ]