Active Noise Canceling

Popularly called simply “noise canceling,” this is a method for reducing noise by adding a sound to the desired signal specifically designed to cancel the unwanted noise. Usually this is done by capturing the unwanted noise but with its phase or polarity inverted. By a process called “destructive interference,” the captured noise and the original noise are combined and the out-of-polarity signals cancel each other out, eliminating the unwanted noise. Active noise canceling has many applications but is most popular today in headphones designed to block out external sound.