Welcome to ‘Kagoo Explains’ - a series of short articles explaining some of the confusing terminology used to describe technology. This week we’re looking at headphones, and the difference between passive noise cancelling (AKA noise isolation) and active noise cancelling.
Headphones are the perfect way to escape reality - but reality has a nasty habit of sneaking back in when you don’t want it to. Sitting on the train listening to quiet country music can be ruined by a loud conversation next to you, or your podcast interrupted by a truck passing by as you walk.
The solution to this is noise cancelling - a technology that seeks to remove the annoying background noise from your listening experience, leaving it blissfully quiet and uninterrupted! When looking at our headphones, you’ll see mention of both ‘passive’ and ‘active’ noise cancelling - these are actually two extremely different systems with very different results.
Passive Noise Cancelling
Also known as noise isolation, passive noise cancelling relies on providing a physical barrier between your ears and the outside world. This can be achieved by tight-fitting earcups that cover the whole ear, or by rubber tips that are placed directly into the ear canal, providing a tight-fitting seal. The result is the same - in effect you are placing earplugs with your music and your ears on one side, and the rest of the noisy annoying world on the other.
Passive noise cancelling has no tech behind it - therefore it requires no extra power and has no working parts to go wrong. However, it is far less effective than active noise cancelling - noises will be dulled rather than removed altogether, and sufficiently loud sounds may still penetrate the noise isolation and disturb your music. Still, it’s better than nothing, and many headphones and earphones are built with some passive noise isolation in mind.
Good value for money
No power requirement
Unlikely to go wrong
Modest noise reduction
Active Noise Cancelling
Active noise cancelling is a different beast altogether, which uses technology to analyse and ‘neutralise’ the sound, leaving you with silence. Here is a brief rundown:
At its most basic, sound is a pressure wave with peaks and troughs - the exact makeup of this wave denotes both the sound and the loudness of the noise. Noise cancelling headphones use a tech known as ‘active noise control’ - they monitor the external noise coming into the headphones, and generate a pressure wave with exactly the same volume, but completely opposite peaks and troughs (known as ‘antiphase’).
When these two waves combine, they effectively cancel each other out, leading to silence - a process called ‘interference’. This allows noise cancelling headphones to entirely block out all external noise, leaving you to enjoy music free of absolutely all external distractions.
It’s a bit complicated, but if you’re interested you can read up more details here. The important thing is the active noise cancelling is far more efficient at removing unwanted noise than passive noise cancelling - however they require far more technology, in the form of the microphone to record outside noise and the processor to analyse and generate the anti-phase. This means that they can only be built into larger sets of headphones - smaller earphones require a whole separate segment for the noise cancelling tech.
Excellent noise reduction
Very good at removing mechanical noise (engines etc.)
Need power source / batteries
Active noise cancelling headphones are also far more expensive than passive ones - you will be paying a premium for an uninterrupted tube journey every morning. However, for many people that is a price worth paying - I know I owe my sanity to a good pair of Sony WH-CH700s blocking out the noise of the Northern Line!
Ready to get a pair of noise cancelling headphones and block out the world? Start shopping our best noise cancelling headphones