How do noise canceling headphones work?

Man wearing headphones with guitar on his back in subway station


Active noise cancellation (ANC) is one of the top features shoppers look for in headphones, but what exactly is it?

As the name suggests, ANC works to actively cancel out background noise that interferes with the sound you hear from the headphones themselves. It can be great for locking and blocking.

Noise Canceling Headphones or headphone can help reduce distractions, but have you ever wondered how they really work? Are you listening to them or are they listening to you? Read on to learn more about the audio technology behind silence.

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Sound waves: Peaks and valleys

Visualization of sound waves

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Before talking about headphones, let’s start with the basic science behind hearing: sound waves. Moving through the air to our ears, sound waves carry everything from the squeak of the morning subway to the subtle “click” as we type.

Like regular waves, sound waves are made up of many different peaks and troughs that together create the noise we ultimately perceive.

The peaks and troughs of sound waves, when combined with an analog pattern, can amplify sound. An example is when you are at a concert and everyone is singing the same song with relatively similar pitch, so it sounds like one voice. This phenomenon is often referred to as constructive interference.

On the other hand, when the two peaks and troughs of the sound wave oppose each other, instead of amplification, there will be cancellation. This phenomenon is called destructive interference, and the result is silence. That’s when noise-canceling headphones were born.

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How ANC headphones listen to create silence

Now, let’s talk about how ANC headphones use the structure of sound waves to bring you peace and quiet.

Equipped with tiny microphones either inside or outside of the earcups of the headphones, ANC headphones listen to your surroundings as much as you listen to the sound they’re playing.

When microphones detect noise, they emit “noise-proof” sound waves that contrast the top and bottom of the incident wave, so you can’t hear outside noise.

how ANC . works

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This destructive interference is why ambient noise is often suppressed when you wear ANC headphones even when you’re not playing music.

Where do ANC headphones work best?

If you’re thinking that it seems like tiny microphones can’t pick up and bounce back on every single disruptive sound wave, you’re right. The sound still comes through.

ANC headphones and overall sound cancellation work best in consistent environments. Consistent environments include airplanes, subways (except for the conductor who is speaking), and in a quiet work environment. Also, some headphones have more efficient ANC than others.

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Frequently asked questions

Noise-cancelling headphones do not block sound waves, but emit reactive waves against the structure of the penetrating sound waves. The opposing top and bottom structure of the two waves leads to silence.

Noise cancellation, noise masking, and noise blocking all seem to work quite similarly, but there are differences. Noise cancellation uses destructive interference with two opposing sound waves to create silence through the built-in microphone. Noise canceling relies on the engineering of the headphone structure itself to hug the ear in a way that prevents sound from entering. Finally, the noise masking feature emits white noise to reduce ambient sounds, hopefully tricking your brain into rejecting sounds altogether.

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ANC headphones work best for sound cancellation when you’re in a controlled acoustic environment like an airplane or a library. Some headphones are also of better quality than others and use more powerful microphones to emit more noise-canceling waves.


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