eli5 Noise cancelling headphones are magical but how does the technology work and does it drain the battery?


eli5 Noise cancelling headphones are magical but how does the technology work and does it drain the battery?

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I’m assuming you mean active noise canceling. You’re in luck because I’m autistic and recently looked into this.

So your headphones have a microphone that “listens” to the background noises and basically plays equal but opposite soundwaves to cancel out the sound. Think about it like this, the soundwave it’s detecting is +2. Your headphones will then play -2. So you’re hearing 0.

It works by having a little microphone right next to the speaker listening for the outside noise that you want to cancel, then playing the inverse of that signal into the speaker, such that the two sound waves should cancel each other out. It can drain the battery more quickly than without since it needs to be doing active processing of the microphone signal to do this.

Does it protect your hearing from continuous machine noise that isn’t too loud?

First off, there’s a big difference between noise cancelling and noise suppression. Suppression works by blocking the outside sound from getting in. This is a passive process. Noise cancelling is an active process, and runs the battery down quicker.

You can think of sound as the air wobbling up and down. (Really, it’s getting squashed and stretched, like thrusting one end of a slinky, but let’s keep it simple to visualise it.) There’s a tiny microphone on the outside of the earphones/headphones. It picks up the external noise that’s going into the ear and copies it, but with an important difference. When the air squiggles up, the speaker plays a down, and vice versa. Basically, it plays an upside-down version of the same noise. When this goes into your ear, the ups from outside cancel with the downs from the speakers, meaning there’s no overall motion.

Sound is basically air movement at different speeds. Sound displace like a 3d bubble similar to the ripple you get when you throw a rock in a lake. If you apply the same force but completely opposite, it will cancel out. Think of it as two people blowing with the same strength a piece of paper but opposite one to each other. The pape sheet wouldn’t move. Noice cancelling has a little mic who listens and inverts the direction (phase) of the sound clashing it with each other getting the same effect. It is pretty magical