How noise cancelling works, and why voices get through

Noise cancelling is two jobs: block sound physically, and cancel what leaks through electronically. Only the second is clever, and it has a weak spot. That weak spot is people talking.

The trick

A microphone picks up the sound, a chip works out the opposite waveform and the speaker plays it. Wikipedia's article on active noise control describes the headphone version: a built-in microphone measures the ambient noise, and an opposing signal is generated to compensate for the part that would still reach the ear. Sound plus its mirror image adds to roughly zero, so you hear less.

More microphones give the chip more to work with. Sony's WF-1000XM6, per SoundGuys, has eight, up from six on the previous model.

Why the low rumble goes first

Wikipedia says periodic sounds, even complex ones, are easier to cancel than random sounds because the waveform repeats. It adds that the most effective noise reduction involves low-frequency sounds, and that engine, propeller and rotor noise is the typical case, since an engine's cycle is predictable.

Wavelength is the other half. Using the 343 metres per second speed of sound that Wikipedia uses, a 100 Hz engine drone is about 3.4 m long. The sound at your ear and at the microphone is nearly the same. At 3,000 Hz the wavelength is about 11 cm, so it changes sharply over a short distance. Wikipedia says sounds above 1,000 Hz tend to cancel and reinforce unpredictably.

What passive blocking does

The earcup or ear tip does the rest, by sealing. SoundGuys' lab data for the AirPods Pro 3 shows it. With ANC on, total attenuation peaks at 43.5 dB at 3,070 Hz. Passive isolation alone peaks at 45.3 dB, at 3,870 Hz, higher in frequency. At that point the ear tip is doing more than the chip.

SoundGuys gives the AirPods Pro 3 a noise cancelling score of 9 out of 10, beating 99% of earbuds it measured, and the Sony 8.8, beating 98% (both read November 1, 2026). Its review figures are a 90% average reduction in loudness for the AirPods and 88% for the Sony. I'd read that as a tie. A seal matters more than the score for most people.

Why voices get through

Speech is a mix of many pitches that change constantly. A vowel sits low, a consonant like "s" sits at several thousand hertz, and neither repeats like an engine. By Wikipedia's logic about repeating waveforms, that makes it harder to cancel. I can't point to a lab test of speech itself, so that part is reasoning.

The measured part is SoundGuys' note on the Sony: the ANC is less effective in the 400 Hz to 2 kHz midrange, so you may still hear some voices and office chatter breaking through.

So the office keeps its chatter and the plane gets quieter. If you want fewer voices, buy a better fit, a deeper ear tip, or a heavier over-ear cup.

What this means when you shop

Low rumble: trains, planes, air conditioning. ANC does its best work here.
Speech and keyboards: fit and passive isolation do the job.

I'd test fit before score. Read the full reviews of the Sony WF-1000XM6 and the Bose QuietComfort Ultra Headphones 2nd Gen, or the AirPods Pro 3 vs WF-1000XM6 comparison. Or browse headphones.