Noise canceling headphones - working mechanism

How do noise canceling headphones work?

Short Answer – what are active noise canceling headphones

When you hear about noise canceling headphones, you are most likely being referred to active noise canceling headphones. These headphones start by sampling the noise around you. They then generate the exact negative of this noise and send it to your ears along with anything else you are listening to. This negative sound cancels out the noise which was sampled. Thus you will end up hearing only the audio you were trying to listen to. In case you were not listening to anything, then all you will hear is blessed silence. This is how noise canceling works should work in theory. Practically though there are a few implementation challenges which we will talk about further in this article.

Introduction – need for noise canceling headphones

The world can be a noisy place. When you are trying to listen to your favorite music while traveling or commuting the sound of traffic or subway noise or the loud roar of an airplane engine can be distracting. These sounds mar your enjoyment of the music you are listening to and also can disrupt your sleep. We all know how precious sleep can be these days and being interrupted while sleeping can be annoying as well as not optimal for health.

While this is the reason for mass market noise canceling headphones, they have been around for a fairly long time. Cockpits of airplanes and helicopters are very noisy places. Along with the noise, pilots need to be able to communicate with others on the radio. In such a scenario, noise canceling headphones are vital for safe communication. Such headsets have been around since the 1950s. For more details, look no further than the Wikipedia page for noise canceling headphones.

Active vs Passive Noise canceling headphones

Alongside active noise canceling headphones, you might have also come across noise isolating headphones. Noise isolating headphones rely on physically blocking out the sources of sound. Noise isolating headphones are cheaper than their noise canceling counterparts but might not do as good a job when it comes to blocking out noise.

Detailed working mechanism of active noise canceling headphones

Lets look at the various components of an active noise canceling headphone.

Noise canceling headphones - working mechanism
Destructive interference in noise canceling headphones

Microphone: A microphone is placed inside the ear cup of the headphone. It listens to the sounds that can potentially be heard by the user.

Noise canceling electronics: The sound captured by the microphone is fed to the noise canceling circuitry. This mechanism analyses the incoming sound. The key characteristics like frequency and amplitude are mapped. After this, an exact negative of the incoming sound is created.

Speaker: The ‘anti-noise’ that is generated by the noise canceling electronics is fed into the headphones speaker. This sound mixes with the audio already being played. The ‘anti-noise’ erases the effect of the external noise but does not affect the audio already being played.

Battery: The noise canceling electronics within the headphones require power to do their job. In most cases, this is accomplished by having a rechargeable battery pack in the headphones.

Check out a BBC video on the working mechanism of noise canceling headphones.


Benefits of active noise canceling headphones

The unit of measurement of sound is called decibels (dB). For reference your alarm clock probably has a sound level of 80 dB and city traffic inside your car probably has a similar sound level as well.

Noise canceling headphones can provide a noise reduction of upto 20 dB. Each brand also advertises the level of noise cancelation provided. Noise canceling as a mechanism works well for sounds which are at a low frequency. Airplane engines and ambient traffic are two good examples of low frequency sound. However, shrill sounds like that of a baby crying or pop music are high frequency sounds and will not be blocked out well by your noise canceling headphones. Considering this, the most frequent usage of noise canceling headphones is by users who need to travel on airplanes frequently.

Some of the benefits of noise canceling headphones are

  • Can help you concentrate when you are in loud places
  • Can help you in sleeping better
  • Can help prevent hearing damage in very loud situations

Drawbacks of active noise canceling headphones

Along with their many benefits, noise canceling headphones do have some drawbacks. The first is that noise canceling headphones are more expensive as compared to regular ones. They also need to be charged since the noise canceling mechanism requires power. While they do block out low frequency sounds, they are not that effective when it comes to high frequency sounds.

To summarize, the drawbacks of noise canceling headphones are

  • Higher cost
  • Need to be charged
  • Not effective against high frequency sounds

Conclusion – are active noise canceling headphones worth it?

If you are a frequent traveler and need to get your sleep while traveling in airplanes, noise canceling headphones can be a godsend. They will help you in sleeping better and you will wake up more refreshed. If you are an audiophile and are looking for high quality headphones with the noise cancelation not being as important, then you can probably give them a miss. Noise isolating headphones might be what you are looking for.