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 AAA battery. Silence outside sound with Sony.