Active noise cancelling (ANC) is different from noise blocking/isolating, which passively blocks both high and low-frequency noises.
This headphone guide explains what the active noise cancelling (ANC) is and how the active noise cancelling headphone works. It will not only help you understand ANC but also help you choose proper active noise-cancelling headphones.
Active noise cancelling (ANC, aka active noise control) is a set of audio technologies that actively cancel the ambient noise.
Both the annoying noise and music reach your ear as sound waves transmitted through the air.
So, one simple way to reduce noise is to physically and passively block it. For example, there are many soundproofing materials and technologies.
In the airport, you may notice ground staff are wearing earmuffs to block the engine and other noises. In the shooting clubs, it is also common that earmuffs are used.
Active noise cancelling (ANC), on the contrary, uses negative sound waves to actively cancel the noise.
This means ANC requires at least three components:
When the ambient noise is cancelled, you will get a quieter environment for your music.
Active noise cancelling (ANC) is still evolving, especially on how to sample ambient sound, how to analyze the sampled ambient sound, and eventually how to effectively cancel the low-frequency ambient noise in real-time.
Please note, active noise cancelling (ANC) currently is most effective for low-frequency noise only.
As discussed earlier, noise can be “blocked” (passive) and/or “cancelled” (active).
Most headphones, in-ear or on-ear or over-ear, can block certain ambient sounds. For example, some in-ear headphones are designed to seal the ambient sound (e.g., Sony WF-1000XM series and Apple AirPods Pro). Of course, over-ear headphones usually can block more ambient sound.
A few vendors may choose “open” designs with ANC earbuds (e.g., Samsung Galaxy Buds Live) to make you more comfortable when wearing them. In this case, noise isolation is minimal. ANC needs to do more work.
For headphones, some manufacturers may also refer to noise-blocking as noise isolation.
Anyway, the differences between active noise cancelling (ANC) and passive noise blocking (or noise isolation) are obvious.
Although different manufacturers may use different algorithms and technologies, they all try to mainly cancel the low-frequency ambient noise.
However, noise-blocking or noise isolation will always block all frequencies.
To cancel the ambient low-frequency noise, the control unit in noise-cancelling headphones must generate sound waves.
Of course, the power source is also used to analyze the sampled ambient sound. While noise-blocking (noise isolation) relies on physical barriers made by noise-isolating and absorbing materials.
All headphones have a certain capacity for blocking ambient noise. Most noise-cancelling headphone manufacturers also try to improve the physical blocking or isolation of ambient sound as well.
Anyway, if you need a headphone with noise-cancelling, you should not be fooled by noise isolation claimed by a few manufacturers.
In addition, a lot of Bluetooth headphones may also claim the noise-cancelling feature. However, such noise-cancelling usually refers to the microphone input, not ANC. You should not be misled by such claims/features.
As mentioned, in any headphones with ANC, there is at least one (usually 2) microphone dedicated to ambient sound sampling.
These sampling microphones normally were positioned outside of the active noise-cancelling headphone. For example, for over-ear headphones with ANC, the sampling microphones are usually on the outside of the cap (for example, Bose 25). It is possible to put such microphones inside the cap. Theoretically, this sounds better. But in reality, it is a bit complicated because the music is also pushed to the same region.
The ambient sound is continuously sampled. The sampled sound waves were processed in the ANC unit in real-time. The delay usually should be in the order of a few milliseconds.
This ANC unit is the brain for noise cancelling in any active noise-cancelling headphones. Different vendors may use entirely different technologies and algorithms to generate a negative sound wave based on the sampled ambient noise.
The generated sound was then superimposed on your music. So, when the sound wave reaches your ear, the ambient noise is effectively cancelled. Most branded active noise-cancelling headphones, for example, Bose 35, or Sony WH-1000XM3, currently can reduce the ambient low-frequency noise up to 80-95%; Apple AirPods Pro can block up to 50-80%.
Please note, the popular Samsung Galaxy Buds and Galaxy Buds+ does not have ANC. It can only block some noise. The later version of Galaxy Buds Live, Galaxy Buds Pro, and Galaxy Buds 2 do offer decent ANC.
If you have any questions on active noise cancelling (ANC), or if you have any questions on active noise-cancelling headphones, please let us know in the comment box below.
The Headphone Guide Pro community will help you find the answer.
Other active noise cancelling headphone guides can be found in the Noise-canceling headphones section.
You may check Headphone 101 for detailed explanations of headphone technologies and terms.
For Bluetooth headphone guides, please check Bluetooth headphones section.
Sports headphones section is dedicated to guides on sports headphone.
Are you considering a wireless earbud? You should check our wireless earbuds guide section.
This post was last modified on October 6, 2021
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View Comments
I'm interested in blocking speech, but if only the lower registers are cancelled by ANC, then the upper registers will still be present. Why can't ANC block higher frequencies and do you think advances will result in speech blocking before too long?
Not so fast. Current ANC technology is usually limited to 1K Hz or lower. For higher frequencies, the physics of sound is not easily resolved. Most experiments and research are limited to low frequencies, where the physics is more or less established.
For example, in an enclosure, based on experiments and theoretical analysis (I cannot remember the source), to reduce the overall sound level, the distance between the noise source (source 1) and music (source 2), should be small. The higher frequencies require a far smaller distance. This is one of the reasons why no ANC technology can handle 1.5K Hz or above currently.
The good thing is that high-frequency sound waves can be easily (relative to the low frequency) blocked.
Anyway, we have to wait quite a long time to get the ANC technology you want. Currently, the only solution is ANC (active) + blocking (passive).
Simple and good explanation
Question. I am looking for ear buds that will BLOCK the noise in my neighborhood. Dirt bikes, loud music, partying people at night. I would like to wear them in afternoons and at night while trying to sleep. I'm not interested in listening to music with these as I already have wireless earphones for that. Does such a product exist?
All earbuds can "block" some external sound. Noise-cancelling usually cancels the low-frequency noises.
There are a few sleep buds in the market. They can block and "mask" noises. The second generation of Bose SleepBuds is quite good. You can check detailed info on the official website. Many bad reviews were for the first-gen SleepBuds.
The cheap alternative to Bose SleepBuds is Amazfit ZenBuds. It is less comfortable compared to Bose SleepBuds II. But the build quality is decent.
Anyway, the effectiveness and comfort of such buds highly depend on individuals. And they are not cheap. If your budget allows, I would recommend Bose SleepBuds II (just do not buy the first-gen one; the second-gen has II in the name).
Do autos that have ANC ( Acura) cancel sub woofer bass on cabin sound systems?
The ANC in most car audio systems usually cancels the engine noise only
However, because the noise to be cancelled is in the low-frequency range, this may affect the low-frequency sound. As a result, you may feel the bass is cancelled.
It is normal for ANC. In most cars, you can turn off the ANC or change the EQ (boost the bass).