HomeTechnologyComputingHow do noise-canceling headphones work?

How do noise-canceling headphones work?


There’s no question that Active Noise Cancellation (ANC) is the most popular feature on any headset, gracing every spec sheet and advertisement.

To, as the name suggests, actively suppress ambient noise that interferes with what you hear through the headphones themselves, ANC can be great for closing in and blocking out.

Noise canceling earplugs or headphones are a surefire way to drown out distractions, but have you ever wondered how they actually work? Do you listen to them or do they listen to you? Read on to learn more about the sound technology behind the silence.

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Sound waves: peaks and valleys

Visualization of sound waves

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Before we talk about headphones, let’s start with the basic science behind hearing: sound waves. Sound waves travel through the air to our ear, carrying everything from the screeching morning subway to the subtle “click-clack” as we type.

Like regular waves, sound waves consist of several peaks and valleys that combine to make the sound we ultimately perceive.

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

On the other hand, when two peaks and troughs of sound waves face each other, instead of amplification, there is net cancellation. This phenomenon is called destructive interference and the result is silence. That’s where noise canceling headphones come in handy.

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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 give you peace and quiet.

Fitted with tiny microphones on the inside or outside of the earcups of the headphones, ANC headphones listen to your surroundings as closely as they listen to the sound they play.

When the microphones detect noise, they emit an “anti-noise” sound wave that counteracts the peaks and troughs of the incoming wave so you can’t hear the external noise.

how ANC works

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

Where wearing ANC headphones works best

If you think it’s seemingly impossible for tiny microphones to pick up every disruptive sound wave and send out a counterattack, you’re right. Sound still slips through.

ANC headphones and the overall sound wave cancellation process work best in a consistent environment. Consistent environments include airplanes, subways (minus the conductor speaking), and in a quiet work environment. In addition, some headphones have a more effective ANC than others.

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Frequently Asked Questions

Noise canceling headphones do not block sound waves, but emit anti-waves that counteract the structure of the incoming sound waves. The opposing peak-and-trough structure of the two waves results in silence.

Noise reduction, noise masking and noise blocking all sound like they do pretty much the same thing, but there are differences. Noise cancellation uses destructive interference with two opposing sound waves to create silence through built-in microphones. Noise cancellation relies on the technique of the headphone structure itself to enclose the ear in a way that prevents sound from entering. Finally, noise masking emits white noise to reduce ambient noise, hoping to trick your brain into canceling the sound altogether.

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ANC headphones work best for noise reduction when you are in a controlled sound environment, such as an airplane or library. Some headphones are also better quality than others and use a stronger microphone to emit more anti-noise waves.

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