Active noise cancellation (ANC)
A technology that uses microphones and a real-time inverse audio signal to cancel out ambient noise in headphones and earbuds. Most effective on low-frequency, steady-state noise like engine rumble or HVAC hum.
Active noise cancellation (ANC) works by listening to ambient sound through one or more microphones, generating an inverse-phase audio signal, and mixing that into the audio you hear. When the two signals collide acoustically inside your ear canal, they cancel — at least partially.
What it does well
- Low-frequency, steady noise: Engine drone (planes, trains, cars), HVAC fans, server-room hum. ANC routinely delivers 20–30 dB of attenuation in the 50–500 Hz band.
- Steady commute environments: Open-plan offices and public transit.
See our AirPods Pro 3 vs WH-1000XM6 lab test for measured numbers.
What it does poorly
- Sudden transients: A door slam, a baby crying, a sharp announcement. ANC algorithms need a stable noise pattern to predict, and transients arrive faster than the system can adapt.
- Speech: Voices have rich harmonics across 200 Hz–4 kHz. ANC attenuates the low end of speech but rarely silences it. This is by design — for safety — and because true speech cancellation requires beamforming-grade DSP.
- High frequencies above 2 kHz: Largely beyond ANC's working range. These rely on passive isolation (the seal of the earcup or ear tip).
ANC vs. passive isolation
A well-sealed in-ear monitor can deliver 25–35 dB of passive isolation across the spectrum without any electronics. A loose-fit earbud with ANC may deliver only 15–20 dB total. Fit matters more than circuitry.
Transparency mode
The inverse of ANC: the headphones pipe ambient sound into the audio path so you can hear surroundings. Modern transparency modes are tuned to feel acoustically transparent ("as if the headphones weren't there"), which is harder than it sounds and is one of the spec axes where premium headphones genuinely earn their price.