ProTech NoiseBuster ANR Headphones rrp $124 BRAND NEW

Low-frequency noise generated by engines, motors and fans is very difficult to attenuate because the noise waves are long, can travel great distances and can penetrate passive barriers, even cement walls. Active Noise Reduction (ANR) is the only effective method of attenuating low-frequency noise. This technology is also commonly termed Electronic Noise Cancellation (ENC), Active Noise Cancellation (ANC) or “anti-noise”. ANR is achieved by electronically coupling a noise wave with its exact mirror image, thereby canceling the noise.

A NoiseBuster ANR system uses a microphone inside the ear cup (1) to listen to noise coming into the ear (2). Using electronics (3), the system takes that information and uses it to create a noise wave that is identical to, but directly opposite of, the one coming into the ear. The ‘anti-noise’ wave is output through a speaker (4), also located in the ear cup. When the two waves (the noise wave and the anti-noise wave) meet, the noise is significantly reduced (5).

More info at http://www.noisebuster.net