This is how Noise Cancelling Headphones really work

Virtually every high end headphone that will be released in 2018 is a noise cancelling headphone . Enjoy your favourite undisturbed jams in any place. On the train, bus, on the street, with your mother, in the gym , with your girlfriend. Noise cancelling headphones that filter out ambient noise are you best friend . But how does this technique actually work?

Noise cancelling headphones

Bose has not been the only one for some time now when it comes to noise cancelling headphones. Sony, JBL, Skullcandy, Sennheiser, Porsche and Bang & Olufsen are a selection of brands that have also started using these techniques. In short: it is becoming increasingly popular. And rightly so, it is a pleasure to be able to isolate yourself from the crowds around you.

Active and passive noise reduction

When it comes to noise reduction, there are two types: active and passive. The passive suppression is all the insulation of the headphones which fit over the over-ear shells, so the thing itself. The active noise reduction gets called noise cancelling.

And how does that work?

The operation is fairly simple: the headphones produce an identical anti-noise of all the sound that is signalled from outside. As a result, the sounds cancel each other out, so that the outside noise is filtered out. So when you are on the move with noise canceling headphones, you hear nothing but your own nice tunes. Great for flying, on the train, gym or at the office.

Digital Signal Processors

In other words, DSP, are processors made to do no less than one task: converting audio to digital sound and vice versa. Noise cancelling. How does that work?

Here it comes:

1. All the sound from the environment is recorded in the headset by a microphone.
2. DSP converts this into digital sound, which happens in no time.
3. The polarity of the sound waves is converted by the DSP: the pluses become minuses and the minuses become pluses.
4. The ‘new’ inverted sound is again converted to analog sound waves and added to the original sound of the environment.
5. Result : silence. Or something that resembles that, because certainly not every brand manages it completely still.

Precise work

The work that the DSP has to do is very precise. Even a mini shift in the sound wave of the back noise can already cause a malfunction. That’s why noise cancelling works the best at low frequencies. These are tones that move up and down ‘slower’ and are therefore more easily picked up by the DSP, think of background sounds. This also applies to monotonous sounds such as the noise of the aircraft engine.