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How Do Active Noise Cancelling Headphones Work?

Traveling on a plane or riding a bike while trying to listen to music can be an annoying task. The ambient noise from the wind or the engines can ruin your listening experience. In fact, the effect is even more pronounced when you’re talking on the phone. Trying to decipher what the other person is saying through the noise can be tough, especially if you’re hard of hearing.

Luckily, noise canceling headphones effectively filter out the noise so you can hear the desired audio. You’ll find it ironic that this audio equipment can also create silence so you can enjoy the sounds you like. They are incredibly useful on planes, in offices, and in other crowded places. As a matter of fact, you can even wear them to enjoy some silence without any audio.

What Are Noise Cancelling Headphones?

Headphones that cancel out the noise and allow you to enjoy your desired audio are called noise cancelling headphones. They are available in two types: Active and Passive. Most on or in-ear headphones are already passive noise cancelling as they physically block outside noise.

The materials used in these headphones are sound-proof. Nevertheless, to be truly passive noise cancelling, headphones need to include a circum-aural construction. This kind of construction includes dense foam layers that filter the noise to the greatest extent.

On the other hand, these headphones are often heavier than others due to the dense materials involved in their construction. In addition, the noise filtering isn’t too enhanced either.

If you’re working with heavy machinery or traveling on a plane, these can often fail to filter out the noise. These serious limitations left true audiophiles wanting for something more advanced. Enter the active noise cancelling headphones.

Active Noise Cancelling Headphones

Active Noise Cancelling headphones are much more advanced than their passive counterparts. They create a barrier against high and low-frequency sounds that might be a nuisance to you. In fact, some headsets that include a microphone that actively cancels noise for the mic as well. This way, the person on the other end hears less noise as well.

How Do They Work?

These headphones work by creating a barrier of sound against noise. They do so by generating an exact replica of the noise with just a single difference. The difference is that the replicated sound wave is 180 degrees out of phase with the original wave.

If you’re aware of acoustics, then you might already know that this leads to destructive interference.

Destructive Interference: The Working Principle

Destructive interference works when two identical waves coincide with each other. It is important that the waves are completely identical in all respects but one. They have to be 180 degrees out of phase with one another. With sound waves, this means that the rarefactions of one wave line up with the compressions of the other.

This results in the sound waves cancelling out each other. Thus, you don’t hear that sound. Active noise canceling headphones work on this same principle. When the replicated and original sound wave coincides with each other, they subtract each other so you don’t hear any noise.

Components

How exactly do these headphones recognize noise? There are a number of components that help achieve the noise canceling effect. These include:

Microphone:

A microphone is embedded inside the ear cup. This microphone listens for external noise that is not blocked out by the headphones. 

Active Noise Cancelling Circuits:

ANC circuits or chips take note of the noise recorded by the microphone. They then work on replicating the sound wave so that all aspects are the same except for the phase. This sound wave is called the ‘anti-noise’.

Speaker:

The speaker then plays out the audio with the anti-noise. The anti-noise effectively cancels out the ambient noise so you’re only left with the normal audio.

Battery:

The circuits need energy to generate the anti-noise waves. This is done through a rechargeable battery.

The Result

Using these principles and components, active noise cancelling headphones provide an additional reduction to noise of about 20 decibels. This makes them ideal for airline travel and offices where you might not be able to enjoy your audio in peace.

Frequently Asked Questions

If you’re still confused, here are some FAQs that hopefully quench your thirst for answers.

Q: Are there any drawbacks to these headphones?

A: While they do a great job of muffling sounds, some individuals argue that canceling noise to such an extent might be dangerous in some situations. Another argument against them is that they cause changes in air pressure.

Of course, choosing when to use them is your own personal preference. Some modern versions include air vents that trap air behind the cups to maintain adequate air pressure.

Q: Do they block out all sounds?

A: The simple answer is no. While they do reduce them to a great extent, they fail to completely block out the noise. Consistent noises such as jet engines or car engines are easier to block than chatter and other abrupt noises. This is because the mic takes time to process the noise which might result in delays.

Q: Do they affect the sound quality?

A: Yes, they do result in a bit of distortion in the sound quality. Your audio might have a background hiss to it. This is why most audiophiles prefer the passive ones over these. You will notice the improved sound quality when you turn off the active noise canceling effect.

Q: Which are better? In-ear or Over-ear ANC headphones?

A: Over-ear headphones are generally much better at canceling out the noise as they completely cover the ear. One can say that they combine ANC and PNC effects in the best way possible.

Parting Notes

All in all, Active noise cancelling headphones use destructive interference to eliminate noise for an excellent audio experience. Not only do these headphones reduce noise, but they also block out low-frequency sounds which are often a cause of fatigue.

You can wear them on their own without listening to any audio just for some peace and quiet. Sometimes, silence can be the perfect music to your ears.

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