Active Noise Canceling Headest   Headphone with built-in Media Player   Flash Pen         Docking Station   Docking Station Media Player     SD Media Player   3.5"HDD Media Player     2.5"HDD Media Player Specifications: • Industrial Active Noise Canceling Headset • Equal amplitude anti-noise of opposite phase canceling outside noise • 40mm NDFeB magnet Speaker (32Ω) • Frequency Response of Speaker: 40 ~ 20KHz • Sound pressure level (SPL): 103.6dB±3dB • Frequency Response of ANC circuit: 40Hz ~ 20KHz • Maximum Active Noise Reduction Level : more than 15dB at 100Hz • Active Noise Reduction Active Range: 40Hz ~ 500Hz • 6dB ~ 35dB in the range of 40Hz ~ 10kHz • Weight: 300g• 20ft: 6,080 sets• 40ft: 12,960 sets