So what I am trying to ask here is whether noise-cancelling headphones are actually working because the listener hears both, the noise-cancellation acoustic wave as well as the original acoustic wave, at once which synaptically cancels out to silence or because the ossicles don't transmit any vibration if both acoustic waves would move the bones in contradicting directions?

Let's assume there is a listener with hypothetical noise-cancelling headphones that cancel out any acoustic wave of any amplitude and a nearby source of acoustic waves with very high amplitude. Which of the following effects is closest to what will actually happen:

  • The listener's hair cells in the inner ear are damaged and both acoustic waves are transmitted by the ossicles
  • The listener's ossicles are damaged because the energy of the contradicting air vibration of the acoustic waves discharges onto the ossicles
  • The listener's hearing is unaffected and nothing is damaged because there is no air vibration when acoustic waves of opposite amplitudes pass through the same space
  • (The acoustic waves cancel each other out before they even arrive at the ear canal)

Please excuse me if I have used incorrect terminology, I am not an expert in either of the topics. Additionally, I am unsure if this is the right stack exchange site to post this question on but since it's mostly about acoustic waves I thought it would fit best here.


1 Answer 1


So-called "noise-cancelling" headphones work by generating a sound signal inside the headphone space which is 180 degrees out of phase relative to a sound source leaking in through the walls of the headphone from outside. This physically cancels that sound signal before it can enter your ears. This does indeed protect your ears from dangerously loud sound signals.

  • $\begingroup$ Just a short addition to the answer. One should keep in mind that the high sound pressure waves will be attenuated (not completely cancelled out but still attenuated), but the negative impact such a high pressure sound has on the rest of the body will not be cancelled. Some negative effects of (usually quite "long-term") exposure to high pressure sound on the body (not necessarily received directly by the ears) have been presented by the World Health Organisation (WHO). Just wanted to add this wee bit to an already very clear answer :). $\endgroup$
    – ZaellixA
    Commented Feb 6, 2021 at 9:38

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