The Koss Quiet Zone QZ PRO Headphones feature both active and passive noise cancellation. For passive noise reduction, The QZPRO features soft leatherette, closed cushions, which create a tight seal around the ear and reduce ambient noise. Active noise-cancellation circuitry uses tiny microphones that sample surrounding noise and transmit that information to a processing circuit, which counteracts the unwanted noise to create a quiet listening environment. Two AAA batteries are required for active noise cancellation and the noise-cancellation feature can be easily turned off with the flick of a switch. The Koss QZPRO deliver a frequency response of 40 Hz to 20 kHz, providing the listener with both deep bass and a balanced midrange.