They block out the screech of train brakes, the hum of an AC unit, or the roar of a jet engine, reducing otherwise ear-splitting sounds to an almost-pleasant background hum. Even as I write this sentence, I\u2019ve got noise-cancelling headphones blocking out the dulcet tones of my coworkers\u2019 conversations. In this post, let’s take a look at how noise cancellation works.<\/p>\n
Technically, all headphones have some sort of capability for passive<\/strong> noise cancellation<\/strong>. If the headphones go all the way over your ears, they physically block out some of the vibrating air that would otherwise be entering your eardrums for your brain to interpret as unwanted noise. Even something as simple as sticking a cotton ball in your ear qualifies as a form of passive noise cancellation.<\/p>\n When we refer to noise-cancelling headphones, typically we’re talking about a technique known as active<\/strong> noise cancellation<\/strong>. Active noise cancellation, frequently abbreviated as ANC, has a number of applications outside of consumer audio. That said, for our purposes, let\u2019s focus on how active noise cancellation is deployed in the context of headphones.<\/p>\n To understand how active noise cancellation works, let\u2019s think about what noise is. The signal<\/strong> that the listener wants to hear is coming from the sound source through the headphones, and the noise<\/strong> is anything coming from outside that might interfere with the listener\u2019s ability to hear the signal.<\/p>\n