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How Do Noise-Cancelling Headphones Work?

Not all headphones are created equal. There’s a whole segment of the market for headphones devoted to cancelling out noise. If you’re a music lover, perhaps ambient background sounds have ruined or interfered with the sounds you’re trying to enjoy through your headphones.

Think about the last time you took a flight anywhere with your MP3 player and your playlist ready to go.

The engine roar can really interfere with what you’re trying to hear, even when it’s being blasted directly into your ears.

Even the voices of other passengers can be disruptive too. Wouldn’t it be nice to tune things completely out and drift off to sleep listen to your favorite songs? Or a mindful meditation set?

That’s where noise-cancelling headphones come in. They can enhance your listening experience, making it far more enjoyable. But there’s more to it than that.

Before you order a pair of noise-cancelling headphones, you should know they come in two different types: active or passive.

Quite simply, all headphones on the market give you at least a little passive noise reduction. The materials that the headphones are composed of block out some of the sound waves around you, particularly those at higher frequencies.

Circum-aural types are noted as the best passive noise-cancelling headphones because they are built specifically to maximize the filtering of noise.

In other words, they have layers of sound-absorbing materials like high-density foam. This makes them a bit heavier than ordinary headphones.

That extra weight is worth it though for getting you 15 to 20 decibels of noise reduction. Jet engines run 75 to 80 decibels though while inside the cabin of the plane, so passive noise-cancelling headphones aren’t all that helpful when you’re traveling by air. This is why you might just consider investing in a pair of active noise-cancelling headphones.

What Are Noise-Cancelling Headphones?

Noise-cancelling headphones help you dampen out any ambient noise around you, allowing you to enjoy listening to music or even keeping focus on talking to someone. They’re useful in noisy places and for those that travel frequently, they can make all the difference on a long-haul flight packed to the gills with crying babies, engine noise, and other distractions that prevent you from relaxing.

Trying to listen to that audio book? It can be taxing to try to get into it when all the noise around you is pulling you away from the experience. Noise-cancelling headphones can be the answer to your needs. But since there are two types of them as we mentioned above, active and passive, it’s important to understand what that means for you so you can choose the most suitable pair of noise-cancelling headphones.

How Do Noise-Cancelling Headphones Work?

How noise-cancelling headphones work depends on whether you choose active or passive versions. For the active noise-cancelling headphones, they basically use a noise cancellation to counteract the other noise you hear. So they create background sounds like the engine roar from your trusty airplane or the deep rumbling of the subway train as well as other sounds.

It’s what’s referred to as ‘anti-noise’ which serves to cancel that unwanted noise in the background. These come with a built-in audio processor.

This detects those sounds and then creates opposite wave patterns. With passive noise-cancelling headphones though, they block out sounds through built-in sound isolation with specific materials.

While it seems strange to use a piece of technology to create quiet instead of noise, you will find that noise-cancelling headphones can be the game-changer you need when you travel or if you sit in a crowded office where everyone is carrying on their roles on the phones with clients all around you.

You may even find them useful if you can’t sleep due to thin walls in your apartment that allow you to hear your neighbors very unsavory activities, your puppy barking, or even in your own bed, to drown out the sounds of your sleeping partner.

This fantastic piece of modern technology works in several different ways. Keep reading to learn more!

Let’s delve more into what passive noise-cancellation means. In order to be successful at controlling noise, noise-cancelling headphones need a form of passive noise control.

Sometimes this is in the shape of your ear buds or headphones to help prevent sound waves from reaching your ear drums in a physical way. These are often referred to as ‘noise-isolating.’

Sometimes these noise-isolating headphones work their magic by creating an external seal around your ears coupled with sound-absorbing materials (like high-density foam for example).

Other times, they come in the form of ear buds that fit into your ear. Noise-isolating products like these can block out as much as 20 decibels of background noise.

But as mentioned before, when on an airplane in particular, you might need more than 20 decibels of sound-blocking capabilities.

That’s why active noise-cancelling headphones would be a better choice for you. Active noise control (ANC) was created by Amar Bose (the founder of Bose), so you can thank him for this brilliant invention.

This technology he designed uses what they call ‘destructive interference’ to cancel out any other ambient noise (like the dull, nagging roar of the engines on your overseas flight).

It goes above and beyond simply blocking out those noises, utilizing a microphone that is placed as close up to where sound will enter the ear.

It picks up the frequencies of that incoming noise and then it actively generate a frequency that is precisely 180 degrees in conflict with that unwanted noise, or ‘anti-noise’ to cancel it out.

It’s sheerly brilliant, isn’t it? So using noise-cancelling headphones can reduce the racket by up to 80 decibels, making it your must-have travel accessory.

Noisy environment at work bothering you? Kids won’t stop making a ruckus while you’re trying to get work done in your home office? Annoying roommate situation? Frequent traveler?

For all these scenarios and more, you could do with a new pair of headphones that truly have your back when it comes to keeping unwanted sound down.

Blocking that noise out when you’re trying to relax or concentrate is very helpful, especially when you can’t change your environment, like say on that long flight or at the office where everyone else is also calling their clients and doing their jobs. Bose and Sony rank among the top sellers for noise-cancelling headphones.

There are other great brands too, but understanding a bit more about how these things work can help you make the right choice for your lifestyle. You should know how science and physics play a role in all of this so keep reading.

■ Amplitude

We’ve given a brief explanation of ANC, but a deeper understanding will certainly help you make a better choice when buying noise-cancelling headphones. One thing to know is that there are different aspects of sound. Visualized, sound comes in waves which you can see with the right equipment (like at a studio for example).

The way you hear sound is actually the compression and decompression of the particles through which it flows. Think of it like a ripple if that helps.

These particles vibrate and cause slight changes in air pressure. Those changes are called amplitude. With your ears, you can detect that pressure change and interpret it as sound. The louder the sound is that’s made, the higher the amplitude is.

So, what does this all have to do with you? Hang onto your hats because here’s more about how it works.

■ In-Phase vs Out-Of-Phase

Just above was the science of it. Now let’s talk about how those headphones can cancel annoying outside noise. In short, it has to do with phase and anti-phase.

Basically, if you can recall from your high school science class, you may remember the high point of a sound wave is called the peak.

The lowest point is known as the trough. If you surf, it’s the very same thing and can help add a little more perspective to understanding this.

■ Constructive and Destructive Interference

So let’s have some fun here and say, for example, you take 2 waves and put them on top of one another so the peaks and troughs match up, this is what is known as ‘in-phase’ which creates a larger wave.

For even more fun, if you move one of those waves over just a bit so that the trough matches with the peak of the other one, guess what you get. Anyone? Anyone? You get effective noise cancellation!

That second example is what is known as being ‘out-of-phase,’ and this is how understanding physics can help you choose your new pair of noise-cancelling headphones.

Still confused? If you have little kids, then perhaps you’ve practiced addition and subtraction with them, holding up one finger and telling them, “If I have one finger and I take away one finger, how many fingers do I have left?” Zero is the answer, and that is exactly how this whole thing works.

Now, let’s take that science and apply it specifically to your noise-cancelling headphones!

The Active Components That Make Noise-Cancelling Headphones Work

We’ve discussed quite a bit so far on noise-cancelling headphones but now we’re going to dissect the components that actively make these things work. Once you understand that, you’ll likely opt to order a pair of them rather than suffer through another flight with inferior headphones.

We’ve talked about passive noise control which basically prevents sound waves from getting into your ears to isolate the noise.

We’ve also talked about the active components that counteract the external noises you would hear without noise-cancelling headphones.

They go beyond absorbing the sound…they make their own ambient sounds to drown out those other ones that you don’t want to hear so you can maintain your focus, whether your goal is work, relaxation, sleep, or anything else.

There are many noisy things to block out so using ANC is the way to go for keeping unwanted noises from interfering. Above, we discussed sound waves and amplitude. Now, let’s apply this lesson to our sound waves.

With active noise-cancelling headphones, you can take an ambient sound wave like the one from the jet engine, and you can take one that comes directly from your headphones.

If you were to graph them out, they’d have the same amplitude and frequency. The difference though is that their crests and troughs are arranged in an out-of-phase manner. So what happens here is those waves cancel each other out.

And that can only happen with the following key components. Tired of our little science lesson? Well, now that’s over but you can apply it to understanding the following things that make noise-cancelling headphones the thing of beauty that they are.

If you’re considering buying a pair, make sure they have these features for your best experience.

■ Tiny Microphones

Remember that destructive interference? This can only be achieved with tiny little microphones built into the outer portion of your noise-cancelling headphones.

These listen and use smart technology to pick up the ambient noise surrounding you. This is then processed as a sound wave so that the headphones can manufacture a sound that is the exact opposite to the sound wave you’re experiencing.

This cancels it out brilliantly and all you ever hear is your favorite band rocking out with pristine clarity.

While this is purely brilliant, science always evolves and things keep getting better. In theory, it works but sometimes, it might not be as perfect as you were hoping it would be.

As an example, the annoying low humming sounds from the airplane’s engines are easy for these headphones to work with and cancel out.

But sometimes, it’ might not be as adept at sudden and random sounds like the flight attendant coming by to ask everyone in your row what they want to drink.

The physics will not change but there are indeed some companies that excel at active noise cancellation. Now that you understand how it works, you can focus on that technology to choose the right pair for your needs.

■ Noise-Cancelling Circuitry

It takes more than the microphone to pick up those sounds and effectively cancel them out. There’s much more to it than that. Inside the ear cup, circuitry senses that input from the exterior microphone.

It creates a map of the noise which notes  the amplitude and frequency of every incoming wave. It then creates a new out-of-phase waves at 180 degrees to counteract that noise.

Consider it teamwork in getting the job done of drowning out that unwanted sound around you.

■ Speakers

That anti-sound that the inner circuitry creates in your noise-cancelling headphones next travels into the speakers with the audio sounds you’re playing, effectively erasing that noise.

Destructive interference washes it away yet it doesn’t detract from your listening experience. In other words, it doesn’t change a thing with the sound waves you want to hear from your headphones.

■ Battery

For all of this to happen, a continuous source of energy needs to function along with it to keep that noise-cancelling effect going strong.

This is why any reliable noise-cancellation headphones all have a rechargeable battery. If you’re looking at headphones and they merely plug into your device to work and don’t have a battery, you should make another selection to ensure you get one that is effective at meeting your needs for noise cancellation.

All of these components together make for the technology behind noise-cancelling headphones. They can add an additional 20 decibels of noise reduction, blocking a good 70% of that ambient noise from interrupting your listening experience.

These will be your new favorite accessory if you work in an open office floorplan where it can be hard to concentrate on your work with the work din around you, while traveling on noisy planes or trains, or in any place that has lots of background noise.

Noise-cancelling headphones are phenomenal with distinguishing between the sounds you want to hear and the background noises you don’t, though sometimes they may lead to muffled sounds.

Changes in air pressure can have an effect too, though the ports built into the ear cups are supposed to vent out air trapped behind those speakers to give you an unobstructed listening experience.

While they might not be fully perfect as yet, if you ask anyone that owns a pair of noise-cancelling headphones what they think, most of them will tell you they’ll never use regular headphones again.

There’s a reason people won’t leave home without them when on their travels. That’s because they help reduce fatigue too.

That exhaustion from constant low-frequency noise exposure over long periods, like on that cross-country flight or when traveling abroad takes its toll.

That hush from the lull allows you to bounce back into your usual self once you do land, helping you feel refreshed and ready.

If you are traveling on business, this can be critical because you’ll be at the top of your game and ready to go.

Advantages of Active Noise Cancellation

With active noise cancellation, the number one advantage of course is the beautiful silence it provides. Sometimes pure quiet like this is the best music to your ears.

When you’re listening to music or using it along with watching videos, you get a better sense of sound quality too though.

Vocals that you didn’t notice before or even softer dialogue in a movie (such as a character muttering something as they walk out of the frame) can be distinguished with noise-cancelling headphones even if you don’t have the volume turned all the way up.

Obviously, if you’re a big traveler, one of the biggest advantages you’ll notice is when you use your noise cancellation headphones on your next flight.

You won’t get that annoying droning sound and that car cabin noise will all blur away. This makes it possible to get some sleep even in cramped quarters.

Take the subway every day, the bus, or any other mode of transport to work and block out those other sounds.

Keep them on at work to stay focused, especially if you’re a creative type too.

Sometimes, creatives need to hear their own inner voices in their heads to do their best work and can’t exactly get that done when they hear the office sounds of the big boss’s secretary cheerfully answering the phone a short distance away.

Disadvantages of Active Noise Cancellation

Certainly, the advantages of active noise cancellation headphones far outweigh the disadvantages, but you should still think about them when making your selection for these headphones.

For some, you may find there is an actual reduction in the quality of sound. The additional sound wave does have the potential to interfere with whatever audio you’re playing through your headphones and can drag down the quality.

You get a less pure sound from it, BUT it should be noted this isn’t always the case with noise cancellation headphones.

It’s why you should use all that information we discussed above to make the right choice in noise cancellation headphones to meet your needs.

Noise Cancelling Headphones Affect Sound Quality

But wait…aren’t noise-cancelling headphones supposed to improve my listening experience? Yes, but that don’t always have a positive effect on the sound quality you get.

For some models, you may experience a very slight hissing sound in the background of your music, giving it a less natural sound.

If you’re the kind of person that needs that pristine quality in your music, you should focus your search on a high-quality pair of passive headphones that go over the ear.

When you turn off the ANC on over-ear headphones, sound quality tends to improve.

Now, which one…in-ear or over-ear? Generally-speaking, ANC noise-cancelling headphones that go in-ear don’t do as effective a job for cancelling out noise.

Over-ear ANC headphones use both active microphones plus the natural shape of those headphones for a dual approach of active and passive sound cancellation.

In-ear tends to be great for passively blocking out the sound but these must fit snugly into your ears for the most effectiveness.

Higher Cost of Noise-Cancelling Headphones

Another disadvantage of noise-cancelling headphones you’ve perhaps already noticed is that they cost more than other headphones.

This is because of those additional components. This is also your clue when comparing headphones to buy that if you find a price that seems significantly lower than the other ones you were looking at, chances are, those are merely wireless headphones without any noise-cancellation technology.

If you don’t mind that they don’t cancel out noise, then by all means! But you’re still reading this which means you have a distinct need for headphones that cancel out noise.

Something else you should know – that battery needs to be properly charged on your noise-cancellation headphones for it to work at cancelling unwanted sounds.

Those key components we discussed above all come into play to fuel the noise-cancellation experience. And one thing you might not realize is this… they do weight more than regular headphones. If you know someone that has a pair, pick them up and you’ll see the difference.

Active Noise Cancelling Can’t Cut Out All Sound

While the term sounds promising, ANC headphones just can’t remove all sound that happens around you.

It’s great for constant, low-frequency sounds, but sounds that aren’t steady will still come through. Think voices or the sound of someone honking their horn in traffic.

Even in the best noise-cancelling headphones when you turn the system on, it creates a bit of a vacuum, pulling you out of the real world.

Some may find this to be what Mrs. Mia Wallace termed in Pulp Fiction to be an ‘uncomfortable silence.’

If you really need peace and quiet on your travels or for your work, you will come to appreciate this deep level of silence in time though it can be overwhelming initially.

In-Ear vs Over-Ear Noise Cancelling Headphones

As a whole, in-ear ANC headphones just don’t do as good a job at noise cancelling. You want to choose ones that go over your ears because they have the full technology incorporated to create an effective ANC experience.

If you don’t care as much and just want a passive way to block out sound, these in-ear headphones like ear buds might be the right choice for you, especially if you want something compact and lightweight. But these will not give you the desired results if you want to cancel out noise actively.

Why Should You Buy Noise Cancelling Headphones?

Not everyone will have a use for noise-cancelling headphones. It really depends on your lifestyle. If you spend most of your time at home where you live alone and it tends to stay quiet, noise-cancelling headphones won’t really make an impact on your life.

However, if you’re always in noisy environments or travel quite often, these will be a worthy investment.

Planes, trains, and buses, or even in a car when you’re the passenger are the best places for noise-cancelling headphones on the go.

They’re also ideal in offices or studios where you don’t want to be distracted. You can even use them for sleep or meditation.

If any of these situations fit your life, you should definitely consider buying a pair of noise-cancellation headphones.


With all the headphone styles out there, it can get confusing making a choice. If you’re thinking about buying noise-cancellation headphones, then you should consider whether they need to be passive or active.

For some, passive will be the right choice. For others, investing into the active pairs is a must.

Remember to focus on the features that make noise-cancellation headphones active instead of passive when you’re comparing them.

This will ensure you pick the right ones that will make all the difference in your life! But do noise cancelling headphones work without music? Read my other post to find out.


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