Passive noise cancellation avoids contaminating the wanted signal that active cancellation risks

Evidence

Both active and passive noise cancelation systems can work very effectively, and many people (including both authors!) tend to prefer the passive type, because only the wanted sound is being presented to the ear and the sound itself is not being modified in any way. In the active case, the wanted signal is having noise added to it—not something one really wants to be doing if one can avoid it. If the phase shift is not absolutely correct, complete noise cancelation will not occur, with the result that the wanted signal is then being further contaminated. Furthermore, because of the phase shift requirement, higher frequencies are not attenuated as effectively—something the passive types do very well. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2568

Categorization

• QUESTION: Worth chasing: does active cancellation’s wanted-signal contamination matter perceptually or only in theory? Under what conditions is the phase shift imperfect enough to matter in real headphones?