Sony's MDR-NC11 Noise Canceling Fontopia Ear-Bud Headphones offer you peace and quiet wherever you go, reducing noise by 70% (10dB) when the noise canceling circuit is switched on. In addition, its 9mm driver units produce powerful sound for your listening enjoyment. So tune out noise at work, when you travel, or even when you are trying to sleep in a loud environment. The Noise Canceling circuit actually senses outside noise with built-in microphones and sends an equal-but-opposite canceling signal to the headphones. The Noise Canceling on/off switch located on the battery box indicates when Noise Canceling is operating. Additional features include the Fontopia in-the-ear design, Volume control, and a Miniature connection box for a battery. Silence outside sound with Sony.