You need an active noise canceling headphone if you want to block the ambient low-frequency noise, like engine noise in the airplane.
Active noise canceling (ANC) is different from noise blocking/isolating, which passively blocks both high and low-frequency noises.
This headphone guide explains what the active noise canceling (ANC) is and how the active noise canceling headphone works. It will not only help you understand ANC but also help you choose proper active noise-canceling headphones.
What is active noise canceling (ANC)?
Active noise canceling (ANC, aka active noise control) is a set of audio technologies which 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 staffs are wearing earmuffs to block the engine and other noises In shooting club, it is also common that earmuffs are used.
Active noise canceling (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 canceling (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, active noise canceling (ANC) system must generate an inverted (negative) sound wave (with similar amplitude) to cancel the low-frequency noise.
When the ambient noise is canceled, you will get a quieter environment for your music.
Active noise canceling (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 canceling (ANC) currently is most effective for low-frequency noise only.
Active noise canceling (ANC) vs passive noise blocking
As discussed earlier, noise can be “blocked” (passive) and/or “canceled” (active).
Most headphones, in-ear or on-ear or over-ear, can block certain ambient sound. For example, some in-ear headphones are designed to seal the ambient sound. Of course, over-ear headphones usually can block more ambient sound.
For headphones, some manufacturers may also refer to noise-blocking as noise isolation.
Anyway, the differences between active noise canceling (ANC) and passive noise blocking (or noise isolation) are obvious:
- Active noise canceling (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. While noise blocking or noise isolation will always block all frequencies.
- Active noise canceling (ANC) requires a power source. To cancel the ambient low-frequency noise, the control unit in noise-canceling 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 canceling (ANC) can be complemented by passive noise blocking (isolation). All headphones have certain capacity of blocking ambient noise. Most noise-canceling headphone manufacturers also try to improve the physical blocking or isolation of ambient sound as well.
Anyway, if you need a headphone with noise-canceling, 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-canceling feature. However, such noise-canceling usually refers to the microphone input, not ANC. You should not be misled by such claims/features.
How does an active noise canceling headphone work?
As mentioned, in any headphones with ANC, there is at least one (usually 2) microphone dedicated for ambient sound sampling.
These sampling microphones normally were positioned outside of the active noise-canceling 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 canceling in any active noise-canceling headphones. Different vendors may use quite different technologies and algorithms to generate the 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 canceled. Most branded active noise-canceling headphones currently can reduce the ambient low-frequency noise up to 80-95%.
Do you know what active noise-canceling (ANC) is and how ANC works in headphones?
If you have any questions on active noise canceling (ANC), or if you have any questions on active noise-canceling headphones, please let us know in the comment box below.
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Other active noise canceling headphone guides can be found in Noise-canceling headphones section.
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