Sennheiser PXC 480 Active Noise-Canceling Headphones NoiseGard active noise cancellation for suppression of plane and train noises. Supplied connecting cable features an in-line microphone and remote for call control. Compact, collapsible design makes it easy to pack for "on the go' use.Impedance:Active 150  / Passive 45  ;Frequency response:17 - 23000 Hz ;Sound pressure level (SPL):109 dB (1kHz/1Vrms) Up to 50 hour battery life providing long listening sessions using active noise cancellation. 2 year warranty when purchased from an authorized Sennheiser dealer. Connectivity Technology: Wired