Noise cancellation is a microphone, a chip and a trick: the headphone hears the noise around you, builds its mirror image, and plays it back so the two cancel. The trick works best on steady sound — engines, air conditioning, the hum of an office — and least on voices, which is why your colleague still gets through.
Adaptive means the headphone chooses how much of that trick to apply. On a quiet street it stays near level one, so you still hear the bicycle behind you. On a plane it climbs to level five. In between it moves without you noticing, which is the whole point: you should notice the music, not the headphone.
If you want to choose for yourself, the app lets you pin a level, and the left cup's button steps through them. Transparency mode is level zero with the microphones turned up: the world comes in, your music stays.
