[squeaky-clean]

What others haven't mentioned and I think is important is that active noise canceling headphones don't try modify your incoming audio. They listen to the outside environment and try to cancel external audio that you'd otherwise hear. For example, listening to a podcast on a noisy bus ride.

This sort of noise canceling tries to remove the unwanted noise that is already mixed in with the wanted sound in the same recording. For example, recording a podcast on a noisy bus ride.