Listen to music or use your smart phone in practically noiseless comfort. Active Noise Canceling (ANC) headphones use an external microphone to pick up background noise and then use sophisticated electronics to cancel it out. To power the electronics, you need a battery. Noise canceling headphones work well when youre trying to eliminate a repetitive drone, such as on airplanes, or the hum of servers, wind, engines or other machinery. Why choose the Konf-X? Active noise reduction (ANC) lets you enjoy a lifelike sound, blocking the noise around. Small yet powerful 9mm drivers, much smaller than competitive drivers, allow for an exquisite rendering of the music. Includes 3 MEMS impedance matched microphones, two are used to cancel out noise and one is for enhanced conferencing. Perfect for making either the professional or casual call, in busy, noisy environments. Can be used without battery (Passive Mode). You can temporarily suspend Noise Cancellation with the Mon button, So you can hear someone talking to you.