How does noise cancellation work

The headphones contain a special noise cancelling circuit which is capable of producing the opposite soundwaves to the sounds that the microphone picks up. This means that the active sound cancels out the background noise so you hear nothing with no need to play music to drown out the background sounds!

If you're wondering how do noise-cancelling headphones work then the video below does a good job of explaining:. In more technical terms noise consists of alternating waves of compression and rarefaction basically decompression or the opposite of compression.

Active noise cancellation works by mirroring the exact compression and rarefactions of the sound waves with exactly the same amplitude volume , the difference between the original sound and the ANC sound is that the ANC soundwaves are inverted. This process causes the soundwaves to combine in a process called destructive interference which forms a new combined neutral soundwave.

It goes without saying that this sort of technology requires batteries, so unfortunately it is not scalable to use for reducing noise in a home as you would require a lot of power read our article on home noise cancelling systems for more information on this , however it is well suited for use in cars or headphones such as the ones below:. The world seems to be getting busier and noisier with every passing day, increasingly it is becoming more and more difficult to find peace and quiet.

Technology makes out homes noisier than ever, busy trains and buses, as well as loud roads and traffic noises, make our commutes noisier than ever and there is no peace to be found in most workplaces. Finding moments of quiet away from the noise is important for our general health and well being. Reducing the amount of sound particularly loud sound in your life will help to improve your health in a number of ways:. Over time these issues can lead to serious health complications.

Taking steps to ensure that your car is soundproofed , your home is well insulated against noise and your working life isn't too noisy can be time consuming and expensive. Using our guitar string as an example again. The frequency is how quickly the string moves through one full vibration.

We perceive higher frequency sound as high-pitched. Lower frequency sound is more bassy. Apart from frequency, waves also have amplitude. Next, the wave also has a phase. This is the position of the peaks and troughs of the wave. If you generate a sound wave that has the same amplitude, but the opposite phase the peaks are where the troughs of the other wave are , it causes destructive interference.

The two waves essentially cancel each other out. This can be done at large scale, where you need to have just as much energy in your anti-noise generator as the original sound itself. Noise cancelling headphones are technological marvels. On the outside of the headphones, there are microphones that sample the ambient noise outside the headphones.

This sound is analyzed by onboard electronics, using a mathematical algorithm. Each headphone maker has its own secret-sauce algorithm, which all work to differing levels of effectiveness. The algorithm is used to calculate the anti-noise wave needed to destructively interfere with the ambient noise where you are.

Then a device known as a transducer, which is essentially a type of speaker, generates the anti-noise wave. Which allows you to enjoy your audio at much better fidelity or just enjoy some peace and quiet. What this term actually means is that a given pair of headphones were designed to block out sound using plain old soundproofing. This means that the materials and design of the headphones isolate you from outside noise to some extent.

They work incredibly well when it comes to constant, predictable sources of noise. Think of a jet engine, the hum of an air conditioner or your fridge compressor. Modern active noise cancellation is incredibly good at erasing that type of sound completely. Conversely, sudden unpredictable sounds pose much more of a challenge.

And why is it so cool? If you try to visualize sound, you probably picture it in the form of a wave like the one pictured above. At least not until you fully understand what it implies. This is where physics kicks in. It may be a little easier to picture sound as a 3D ripple through air. Those moving particles lead to very slight changes in air pressure. We call the measured power of these changes in air pressure amplitude.

Your ears and brain detect and decipher those changes in pressure as sound. If you were to chart the amplitude, over time you end up with the wave pictured above. The louder the sound, the more extreme the amplitude. But what happens if you delay one of the waves by exactly one half wavelength matching up the the troughs with the peaks of the other like in the picture below? Constructive and Destructive Interference. Think of it as trying to add one and subtract one. This is the basic physics behind active noise canceling.

But how is that used in your headphones?