What is ANC in headphones?

Active noise canceling, or ANC for short, is one of the coolest features to come to headphones in recent years. We can combine existing passive noise cancellation with active one for a great external isolation. But to what extent will we achieve this with this technology? Is it really worth having active and passive noise canceling technology? What is the difference between the ANC of cheap and expensive headphones?
In this article, we will answer all these questions and explain how active noise canceling works in headphones in the best way possible. So feel free to continue reading.
Isolation and noise cancellation in headphones
The purpose of both active and passive noise cancellation is to provide isolation from the entire external environment at all times. That is, to ensure that the user is as isolated as possible from what is going on around him.
Therefore, we can intuitively think that this is a bad configuration for those who need to listen to the people around them for some reason. However, there are more reasons. Headphones with good isolation and noise canceling are closed type, on the market we find open and semi-open headphones, they basically have holes outside their capsule, allowing sound to leak out and ambient sounds to be perceived.
Many people prefer open earphones over closed earphones as they usually offer an audio experience with a larger soundstage. To clarify, it means the sound is wider and more positionable, very useful when listening to music, and has a more neutral sound profile. Closed earphones focus more on bass and also offer that isolation that isn’t always beneficial for everyone.
In terms of sound quality, they can be said to be comparable today, so there is not much to comment on. If you’re interested in isolating outside sounds, keep reading because we’ll explain all about active and passive noise canceling.
Passive noise cancellation
Let’s start by talking about passive noise cancellation. This is not a technology per se, but refers to the way headphones are designed. Therefore, by “passive” it is meant that no changes are made to the sound to achieve greater external isolation, but everything is achieved thanks to the design of the headphones.
So each manufacturer decides whether their product is worthy of “passive noise canceling”. There is no certification about it, which leaves it more like a marketing element.
That said, it’s certainly true that headphone design has a tremendous impact on isolation levels. To prove this, let’s take a few examples of closed over-ear headphones and review the RTINGS data table. This is a website with very rigorous and clear headphone tests.
On the one hand, we found that the Corsair Void PRO RGB provides around 5dB of external noise reduction, while the Cooler Master MH630 provides around 9dB of attenuation. Now if we go to models that advertise passive blocking, like the Razer Blackshark V2 Pro, we reach a 13dB attenuation. That’s a difference of almost 10 dB and very noticeable, but the Sennheiser EPOS GSP 600s achieve 20 dB attenuation.
Considering that we are dealing with the same type of headphones, we conclude that design is crucial, so some models qualify as having good passive noise canceling. Now you can achieve much more with active noise canceling. For example, if we go to the Razer Opus Wireless, we get almost 30dB attenuation thanks to ANC (active noise cancellation).
It may seem like a minor difference with Sennheiser, but let’s remember two things: the GSP 600 is an exception in passive cancellation. Generally, passive suppression does not go beyond 10 or 15 dB attenuation. A difference of 10 dB is perceived as twice the attenuation due to how the decibel scale works. So it’s no small thing.
In general, the best way to achieve good passive noise cancellation is with large, thick ear cushions that cover the entire ear and create a separate environment with as little contact with the outside as possible.
Active noise cancellation
Now let’s see exactly how active noise cancellation works and what quality can be achieved with this cancellation. The working principle of active noise canceling is very simple. First, let’s remember two short concepts:
Sound is transmitted in the form of sound waves. Noise occurs when two sound waves of the same frequency combine.
When there is interference, depending on the amplitude of the interfering waves, two effects can occur: either it is constructive interference, because the two waves overlap and both waves combine to give a greater amplitude; or a destructive interference where superposition causes a smaller amplitude wave.
This is best explained as follows. Considering a wave A and a wave B of the same amplitude:
If the crest of wave B coincides with the crest of wave A, the result is constructive interference. It becomes “1+1 = 2”. If the crest of wave B reaches the trough of wave A, then we have a destructive interference where both waves cancel each other out and we get “1-1=0”.
So active noise canceling is about artificially canceling as many sound waves as possible. For this, the headphones have microphones that capture noise from outside and inside and are analyzed by a special processor, which analyzes the captured waves and reverses them to cause destructive interference that leads to complete silence.
The effect of active noise canceling on headphones
Unfortunately, the degree of “passive noise cancellation” isn’t worth much on its own, and so is ANC. And it’s not enough to see that some headphones offer active noise cancellation. Yes, the tech will be there, but there’s an incredible performance difference depending on the headset.
And it’s really hard to implement ANC well. Even the most expensive ANC headphones cannot filter and cancel any sound. So now I will explain what is accomplished with active noise cancellation and what is not, and what is the difference between cheap and expensive headphones.
First, I’ll do it on a personal experience level with hours of use of two headphones with this feature: Sony WH-CH700N (cheap) and Sony WH-1000XM4 (very expensive). We will then turn to the RTINGS data to provide objective support for this section.
As for the personal experience left by the active noise canceling, let’s talk about cheap headphones first. In this case, ANC helps suppress outside noise, but does not change the life. Basically, it serves to reduce the effect of very repetitive and constant sounds like an airplane engine. It doesn’t cancel all of its noise, but it does cancel certain frequencies.
In fact, we should pay much more attention to passive cancellation in cheap headphones. Adding a modest ANC won’t do much if using small pads that barely cover the ear.
An impressive experience is obtained in more expensive headphones. Something comparable or better to a gamer switching from a 60 Hz monitor to a 144 Hz monitor. With the XM4 for reference, you already notice the great effect of good passive cancellation as soon as you plug in the earphones. However, as soon as you turn on the headset, it mutes the environment and changes radically.
Being outside, in a car, in a somewhat noisy place… An incredible effect is achieved. But be careful, because that doesn’t mean it cancels everything. In particular, ANC has trouble canceling vocals and other sounds that are highly variable and close. The key is in proximity and above all physical barriers. A simple action like closing a door or window can change the cancellation level drastically.
Another problem with active noise canceling is possible bias the listener may have when their headphones are on. An example: if you are reading silently with ANC and suddenly you hear the noise of a car, you will notice it and think that ANC is not effective.
In fact, during that time, dozens of cars that you have not even heard of will have passed. But that 90% you can’t hear really makes a difference. Personally, in my early days with the Sony WH-1000XM4, I would regularly take off my headphones to be aware of the enormous amount of noise canceling and thus “train” my mind.
Let’s analyze the effect of ANC in real data

I’ve said enough about my personal history, it’s time to turn to objective data. Let’s reanalyze the ones provided by RTINGS to find out the active noise canceling performance in earphones by price level.
We have selected several models in the segment of on-ear headphones with and without active noise canceling, whether closed, semi-open or open.
As we can see, the performance of active noise canceling headphones has something to do with their price. With the notable exceptions (JBL Tour One on the “expensive” side and Anker on the “cheapest” side) we see a correlation between outstanding blocking performance and headphone price.
The big reference is the difference between the Sony WH-CH710N and the WH-1000XM4, where the latter cost 300 € more, but they also have completely outstanding noise reduction.
When it comes to closed headphones without noise canceling, we see that models with very close prices achieve very different performances. Come on, it all comes down to a good passive noise canceling effort from the manufacturer.
Conclusion and Final Words on Active and Passive Noise Cancellation
For many, the isolation their headphones provide is something plain and simple, essential. Anyone who wants to isolate himself from a noisy environment will find a perfect ally in well-insulated headphones. This is achieved through active noise cancellation and good passive noise cancellation techniques.
Let’s start with passive cancellation. This is not a technology per se, but refers to an effort to increase the insulation of the headphones by changing the design, for example by designing them with a closed capsule and more ear cushions.
But where the magic really happens is in active noise canceling. This technology is based on the fact that two opposite sound waves cancel each other out, resulting in absolute silence. For this reason, headphones with this technology, also called ANC, have microphones that are used to pick up outside noise and give back waves to the headphone, which completely cancels it out.
ANC is extremely effective, especially in more expensive headphones that can completely mute the environment. Of course, these currently don’t work with sounds like very close ones, or with nearby, non-repeating noises in general, and this falls into a frequency range that headphones can’t cancel very well.