How do noise-cancelling headphones work?

February 15, 2011

You asked: How do noise-cancelling headphones work?  

We answered:

Many people think that noise cancelling has to do with physically blocking sounds from outside the headphones; and while this is partially correct, there is also technology that exists to actually cancel-out ambient/background noise (the sound of an airplane's engines, the HVAC system, the buzz of lights being dimmed are all examples of ambient noise).  

Noise-canceling headphones can be discussed under two categories: active noise reduction and passive noise reduction.  Passive noise reduction takes place by physically blocking it by insulating the ear from being able to "accept" incoming ambient noise.  In the case of active noise reduction, the ambient noise is canceled by using electronic technology. The components of noise-canceling headphones include:

  • earpieces that sit around the ear,
  • a noise-canceling circuit, and 
  • microphone(s) that are installed in the earpieces. 

When ambient noise (noise coming from outsie the headphone) is generated, it is recorded by the microphone. The microphone is connected to the noise-canceling circuit which may be set up in such a way that it either blocks the noise completely (both background and directed noise) or allows it to reach the ear. The noise-canceling circuit, then uses the wave property of sound to create an equal and opposite wave that cancels the ambient noise.

In headphones that are branded as "noise-canceling", the headphones both block outside noise by physically blocking the sound and use active noise canceling technology to block ambient noise from interfering.

There are strengths and weaknesses to having noise-cancelling headphones; however, we've found that those who have them find the experience to be extremely enjoyable because the focus is on the audio coming from the headphones, not a mix of sounds outside the headphone & inside.  Those who travel by airplane also have discovered the joy of noise-cancelling headphones, as the ambient noise that comes from the airplane's engines can become irritating and cause discomfort.  The active technology can almost completely block the sound and make the flight more enjoyable.

Gramophone offers a variety of noise-cancelling headphones, both wired & wireless, from Dr. Dre's Beats to Sennheiser's wireless & noise cancelling, and we strongly believe that the best way to find the right pair of headphones for you is to try them out for yourself.