How does noise reduction work?

There are two ways that noise cancelling headsets work, ergo, noise cancellation comes in two distinct forms. The first, known as ‘passive’ noise reduction is actually pretty obvious. For a good demonstration, hold your hand flat (as if you were attempting to ‘karate chop’ something) and then place it over your nearest ear (but don’t hit yourself, of course). Notice the muffling? That is passive noise reduction. By this measure, anything that covers your ears or blocks sound from entering them is a form of passive noise reduction. By this token, then, all headphones and headsets are passive noise reducers. Continue reading