How Do Noise Cancelling Headphones Work

The ambient noise is a very important factor that determines the final quality of the sound headphones, especially if you have a room acoustically isolated and used our headphones in public places. This is when active and passive noise cancellation technology plays an important role.

Types of Noise Cancellation

  • Active noise cancellation: which we will also call active technology.
  • Passive noise cancellation: also known as sound insulation.

The system’s active noise cancellation or ANC (its acronym Active Noise Control) is an active technology to eliminate outside noise. It is achieved by eliminating this “outside noise” thanks to the wave interference theory. Easily explained would be the following:

Sound is a low-frequency wave that complies with the principle of superposition. That is when two or more waves meet at the same point. The resulting wave is the vector sum of the waves that have been found at the same point. Thanks to this feature, an artificial sound wave is created that, if we add it to the original wave, results in the total or partial cancellation of a part of it. This is what is known as destructive wave interference.

In the headphones, we will hear the sum of the original signal (the music) with that of the ambient noise. If the headphones have active sound cancellation, there will be an artificial signal that will cancel out that ambient noise. This artificial signal is nothing more than a sound wave created by an electronic circuit.

how noise cancelling headphones work

How Can An Artificial Signal Cancel Out Only Ambient Noise?

It does this through one or more microphones located on the body of the headset or on the cable that collect the ambient sound. Then process it and generate an equal signal, but of the opposite phase. When this new signal is reproduced together with the signal. Original, the result is destructive interference and sound free from ambient noise.

It is also capable of eliminating sound leaks caused by hair, glasses, ear shape, and head movements.

However, this theory is not totally perfect. Its operation is limited by the main frequencies that make up the noise signal. That is, with low frequency and constant noise produced by a motor it works very well. However, the problem is with high-frequency sounds, but this can be solved with passive techniques. That is, acoustic insulation systems, which we will talk about later. But generally, they work well.

What many people don’t know is that active noise cancellation is a feature that can be turned on and off according to the user’s needs. If we deactivate them, we lower the consumption of the headphones, without losing sound quality.

Disadvantages of active noise cancellation

They are systems that need external power. That is, the headphones have to be charged with a USB connector, with small batteries, or with rechargeable batteries.

It is possible that the same system can slightly modify the final signal. This implies that it degrades the signal or that it can introduce annoying background hiss.

Incorporating this system in a headset increases its selling price.

It is possible, although less and less, that the size and weight of the headphones that carry this system increase.

What is passive noise cancellation and how does it work?

The passive noise cancellation system, also called acoustic insulation, ensures that outside sound does not enter our hearing system. This effect is achieved by placing insulating material between the housing of our headset and the part that will be glued to our ear or ear.

This technology is the simplest and cheapest, that is why, today, it is used in all headphones. However, it is not enough because it only attenuates the outside noise, but does not cancel it.

This feature, although we may not think about it, can also be turned into an advantage. Because we can hear ambient noises that may be necessary for our safety (such as the engine of a car or a bus). Also, they don’t need to charge them in any way either.

The best headphones with this type of system are on-ear and over-ear, also known as supraaural and circumaural respectively. The in-ear (those that are NOT headband), meanwhile, tend to have little passive noise cancellation, especially if they do not fit well to the ear.

Our Favorite Noise Canceling Headphones

It is difficult to choose between so much variety and this list tends to rotate a lot. Because new models are appearing on the market, today they are:

  • Bose QuietComfort 35 II
  • Huawei Freebuds 3
  • Sony WH-1000XM3