You need an active noise cancelling (ANC) headphone if you want to block the ambient low-frequency noise, like engine noise in the aeroplane. For example, Sony WH-1000XM (XM1-XM4) series, Bose Quietcomfort series (e.g., 15, 25, 35, earbuds), Apple AirPods Pro, and Samsung Galaxy Buds Live all have ANC.
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.
What is active noise cancelling (ANC)?
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:
- Power source. Active noise cancelling (ANC) always requires a power source to detect and analysis noise and then generate a negative wave.
- Noise detection. Normally, one or more microphones are used to sample the ambient sound.
- Anti-noise sound wave generator. Once the ambient noise is sampled, an active noise cancelling (ANC) system must generate an inverted (negative) sound wave (with similar amplitude) to cancel the low-frequency noise.
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.
Active noise cancelling (ANC) vs passive noise blocking
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” design 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.
Active noise cancelling (ANC) cancels ambient noise selectively.
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.
Active noise cancelling (ANC) requires a power source.
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.
Active noise cancelling (ANC) can be complemented by passive noise blocking (isolation).
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.
How does an active noise cancelling headphone work?
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 in 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 the 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%.
Do you know what active noise-cancelling (ANC) is and how ANC works in headphones?
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.
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Other active noise cancelling headphone guides can be found in the Noise-canceling headphones section.
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