Anti-noise

Opposing or anti-noise: that is fighting noise with sound

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Anti-noise is a sound that cancels out another sound through an opposite phase. The counterphase can occur through reflection, but can also be consciously generated with electronics and a loudspeaker. With the latter, it is possible to mute existing sound, something that works well, especially at lower frequencies and monotone sounds.

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Less annoying to the human ear:

Low-frequency, monotonous sounds (vibrations) can be combined with other air vibrations. This reduces the pressure variation of the vibrations that we hear in our ear. Anti-noise therefore doesn't really cancel out the sound (that's physically impossible) but it does make it less annoying to the human ear. Anti-noise cannot be used outdoors. It is only suitable for enclosed spaces, especially when it comes to low-frequency noise. It is not the solution for all noise pollution. In addition, it is often used in combination with another noise-reducing approach.

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How do noise cancelling headphones work?

Microphones on the outside of the headphones recognize monotonous sounds. The speakers output the same frequencies a fraction later. The sound waves are thus out of phase and cancel each other out, making that hum or hum a lot quieter. An airplane engine, the express train, the vacuum cleaner, the noisy computers in the office disappear into the background. Other, non-monotone sounds, such as people talking to you or the music you're listening to, are easy to hear. That anti-noise does feel like your ears are under pressure.

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