How Does Active Noise Cancelling Work?

Let’s take a deeper look at the tech that protects your hearing.

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If you are in the market for a decent set of travel headphones, or in some cases even new cars, you are likely to see mention of “active noise cancellation” technology. But what is this tech, what does it do, and should you even care? The quick answers are: it’s destructive cancellation with sound wave, it makes your world quieter, and yeah you should probably care.

But let us skip the quick answers and get into the meat and potatoes.

What is Active Noise Cancellation

At its core, active noise cancellation is the act of receiving sound, analyizing it, and then producing an opposite wave to counteract the sound using destructive interference. It sounds complicated, but the basic science behind it is rather simplistic. All sound is a wave that passes through the air and comes in contact with our ear. When it makes contact, that wave creates a vibration that our brains interpret as sound. Since our hearing depends on that vibration, we can use an opposite wave pattern to effectively “kill” the vibration, meaning that our hears silence.

Think of it like holding a small piece of rope with both hands. If you pull with both hands, the rope doesn’t move. Using opposite forces of equal strength, cancels out the overall force. It’s simple physics, but applied to your ears.

Here is a quick GIF we made from an old video explaining sound phasing.

What this means is that with proper technology to “listen” to the world around you, a good set of headphones can create a “cancel tone” that minimizes the sound you hear. The downside to this technology is that it’s really only effective on constant noises, like the hum of an airplane, or the sound of your neighbor’s lawn mower.

In a pure theoretical world we could use this technology to completely silence the entire world around you, but in practice that is just not effective. We can’t cancel quick, sharp noises like voices or car horns, simply because of the speed of sound. We don’t have the means for a set of headphones to hear a sound, analyze it, and then create a counter tone in the brief millionths of seconds it takes for that sound to pass the distance from the headphones into your ears.

Now that we have most of the boring science stuff out of the way, let’s look at how this can actually benefit you.

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