How Does Noise Cancellation Work?

By Malakhi Beyah, 2025

Published 11/27/2023

Active Noise Cancellation has become a very popular feature in various headphone brands. Photo courtesy of Bose.

Apple, Sony, Bose, and many other technology companies boast selling quality noise-canceling headphones. This prominent feature ensures that the wearer’s music is almost completely undisturbed by outside noise. The experience is comparable to turning the volume down on your surroundings. The appeal of a “mute button” for the world has driven up sales for noise-canceling headphones recently. Many people, however, enjoy this feature without fully understanding how it works. 

The technology behind noise cancellation is somewhat unorthodox. It starts with a microphone built into the headphones that analyzes the sound waves around it. The headphones then counteract the sound waves by reversing them and playing them at the same time as the original sound wave. The reversed sound waves serve as equal and opposite “anti-sounds” that balance out the noise in a process called “destructive interference.” The processors in the headphones must do this quickly; sound travels from the outside of headphones to inside of them in mere microseconds (a millionth of a second). For this reason, improving headphone processors is essential to the effectiveness of noise cancellation.

Users of noise-canceling headphones may have noticed that the feature works on some outside sounds better than it does on others. For example, someone may be wearing noise-canceling headphones next to a car honking its horn while having a conversation with their friend. While the horn will seem muted to the wearer, they will likely still be able to hear their friend speaking to them. This happens because of how the headphone processors generate “anti-sound.” The sound from the car horn does not change in pitch; because of this, its sound waves are more constant, and it is easier for the headphones to match them with opposite sound waves to balance them out. When the friend is speaking, though, every syllable they say has a different pitch. Headphones have more trouble generating opposite sound waves when the original sound waves are so varied. Because the headphones cannot keep up with the changing sound waves from the friend’s voice, more sounds from the voice pass through the headphones unfiltered. 

Noise-canceling technology has permanently changed the way people enjoy music. Listeners can relish the ability to focus more on what is coming through their headphones than all the disturbances around them. As the technology in headphones advances, people come closer to entirely tuning the world out.