Sennheiser - Noise Cancelling Headphones (PXC 450) Type: Noise Cancelling Frequency Response: 8Hz-28KHz THD: Input Impedance: 150/750 ohms Sensitivity: 108dB S.P.L. at 1KHz Cord Length: 4.6 feet Weight: 8.47 oz. Features: Adaptive baffle damping and special Duofol diaphragm technology for pristine audio production. Switchable NoiseGard 2.0 reduces ambient noise up to 90%. Active/bypass mode for use as a noise cancelling or closed-back audiophile headphone. Luxurious materials for long-lasting comfort and exceptional durability. TalkThrough function for easy communication with the people around you while wearing the headphones. Simple-to-use volume control integrated into the headphone. Ideal for people on the move: comfortable, sturdy and foldable headphone design Audio transmission always works â€" even in passive.