How Do Noise Cancelling Headphones Work

How Do Noise Cancelling Headphones Work

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If you’ve ever been on a plane and were almost unable to hear your music or the in-flight movie over the sound of the engines, then you understand the need for noise-cancelling headphones. This amazing technology eradicates ambient noise in a way that regular headphones can’t compete with. Once you learn how they work, you’ll be ready to buy a pair for yourself!

What Are Noise-Canceling Headphones?

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Image via Flickr by VikramDeep

Noise-cancelling headphones are battery-powered headphones that electronically interfere with the noises around you that disturb your listening experience. When it comes to blocking out external sounds, headphones operate in two ways: noise-isolating headphones use passive interference to deaden ambient noise, while noise-cancelling headphones use both passive and active interference.

Passive interference refers to the physical attributes of the headphones. The materials that comprise the best noise-isolating headphones, such as dense foam earcups, can deaden external sound by up to 20 decibels. Most noise-cancelling headphones are made with materials that deaden a small amount of ambient noise even when they’re turned off. But when powered on, noise-cancelling headphones also use active interference: they detect the shapes of sound waves to produce opposing waves that cancel out ambient noise.

How Do They Work?

Noise-cancelling headphones work best when they’re cancelling a consistent sound, like the rumble of a plane, the hum of a furnace, or the quiet growl of a car engine. That’s because noise-cancelling headphones actually produce sound waves to cancel out these ambient noises, and these waves are easier to produce when the offending sound is consistent.

Sound waves come in different frequencies. They can add to each other, to produce louder sound, or they can cancel each other out when their peaks and troughs fall in opposite places. That’s how noise-cancelling headphones work: they produce “destructive interference” which cancels out the offending ambient noise. They use an interior microphone to detect outside noise, and circuitry that plays that sound at the exact opposite frequency, which cancels out the sound waves of those irritating, mostly low-frequency ambient noises, before they reach your ear.

Do They Cancel All Noise?

Even the best noise-cancelling headphones can’t block out all the sounds around you. Random noises, like talking or footsteps, make sound waves that are too varied for current noise-cancelling technology to eradicate completely. However, the best models give you a considerably quieter experience, and companies that use good materials to produce their headphones will still be able to reduce most ambient noise, whether passively or actively. Sony’s top noise-cancelling headphones, for example, give you a total noise suppression ratio of 99.7 percent.

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When Is It Best to Use Them?

Noise-cancelling headphones do wonders when you’re on an airplane. That loud, constant engine noise drops to a low level, leaving you free to listen to your music or audiobooks at a lower volume. You don’t have to listen to anything when you’re wearing your noise-cancelling headphones. If you simply want to drown out the ambient hum of the plane, your air-conditioner at home, or the computer at work, you can do that.

If you’re trying to drown out the ambient noise in, say, a coffee shop, where the hum of the machinery comes punctuated with loud sounds and conversation, don’t expect total silence when you put your headphones on. That being said, they’ll still bring you a considerably quieter experience than you’d get with the ear-buds that came with your smart phone. You can play your music at a lower volume and still hear its idiosyncracies better.

You can buy noise-cancelling headphones in several designs. The over-the-ear design completely covers your ear, creating a shell or a cocoon around your ear with cushioning. The ear-bud design goes in your outer ear canal, and is made of material that completely plugs your ear canal to further reduce ambient noise. Both styles work for noise-canceling purposes, so it’s up to you to decide what you think is the more comfortable headphone design.

Noise-cancelling headphones work beautifully to cancel out the consistent ambient noise around you. They’re especially wonderful on airplanes, but will also provide you with a better listening experience in many other settings. Whether you simply want to sit in silence without hearing the humming air conditioner, or want to experience the depths of your music, a pair of noise-cancelling headphones is for you.