Koss QZ900 Noise Cancellation Headphone (Black) Reduces harmful and annoying low frequency sounds in noisy environments Operates on 1 AAA battery for battery life of 50 hours (Not Included) Cord unplugs to enjoy passive and active noise cancellation wirelessly Folds flat for portability, carrying case included Straight, single entry 4 foot cord with inline volume control Dramatically Reduces Most Low Frequency Distractions From Airplanes, Lawn Mowers, Fans Or Even The Din Of An Office Freq Resp: 20 Hz-20 Khz; Imp: 32_ Operates With Or Without Active Noise-Canceling Circuit Engaged Wired