How active noise cancelling actually works
Feedforward, feedback and hybrid mics, why ANC loves a droning engine, and how much quiet you can expect.
By the Let’s Compare Editorial Team · 1 min read · Updated September 24, 2026
Active noise cancelling (ANC) doesn't create silence. It uses microphones and inverse sound waves to cancel noise before it reaches your ear. Once you know how that works, you know what to expect from it on a plane or a busy commute, and what to look for in a pair.
ANC microphone layouts
| Type | Mic location | What it does |
|---|---|---|
| Feedforward | Outside the earcup | Catches noise before it reaches you |
| Feedback | Inside, near the ear | Corrects the noise that gets through |
| Hybrid | Both | Generally the most effective and consistent |
Three microphone layouts
ANC relies on microphones that listen to noise so the headphones can play an opposite "anti-noise" wave. Feedforward systems put the mic on the outside of the earcup, where it catches noise before it reaches you. Feedback systems place it inside, near your ear, to measure what actually gets through. Hybrid ANC combines both. It's now common on good headphones, and it's generally the most effective and consistent approach.
Steady drones vs sudden sounds
ANC is best at constant, low-frequency sound: the drone of a jet engine, air conditioning, road rumble. Those steady waves are predictable, so the system can generate an accurate opposite. Sudden, high-frequency sounds like a voice or a clatter are much harder to cancel. That's why ANC hushes a plane's roar but won't mute the person talking next to you, and why a good passive seal and physical isolation still pick up the slack.
How quiet it gets
A solid ANC system commonly delivers between 20 and 40 dB of reduction. That cuts the background noise you perceive to roughly a quarter or less of its original level. It's a dramatic drop in droning noise, but it isn't silence, and fit changes the result considerably. On earbuds in particular, a tip that doesn't seal leaks bass and lets noise in, so trying the included tip sizes matters as much as the ANC circuitry.
When you compare headphones, give independent measurements of low-frequency attenuation more weight than marketing claims. And count a good transparency mode, which lets noise back in when you need it, as part of the same feature set.
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Sources & further reading
The facts and figures in this article come from the references below (some of them not in English), so you can check them yourself.