- the active- the passive types.
HOW PASSIVE NOISE CANCELLATION WORKS
The simplest type of noise cancellation is the passive noise reduction, sometimes called noise isolation. From a technical perspective, just about any kind of earphones are able to provide some degree of passive noise reduction (though some are designed for it more than others). This is mostly as a result of the materials used to make the headphones which block out particular sound waves, mostly those of a higher frequency. The absolute best type of passive noise canceling headphones are however the circum-aural types which are specifically engineered to maximize the amount of noise it filters. We will take a look at this some more in a bit. Essentially, where passive noise isolation, the head phones are so designed that they will fit snugly into or around each ear. This makes it significantly harder for noise to escape and bother others in your immediate environment, and it also prevents the noise in your environment from making it hard for you to listen to your music. Passive noise cancellation earphones tend to have very large ear pieces, with large pieces of foam wrapped around them. You need to squeeze the foam into your ear which them provides a perfect seal for the ear canal, or they fit just right around your ear.
All this is saying that passive noise cancelling earphones in essence imitate what happens when you choose to cover your ears with your hands or put some ear plugs in. The excess padding is always done with materials that naturally act as sound barriers- fitting into your ear and sealing off the ambient noise.
Supra-aural headphones, which are earphones placed over and around the ear, instead of in or around it, are probably the very worst at any form of sound cancellation. They tend to be low density, small and very light, as such there is really not much padding to block and outside sound or ambient noise from entering the ear. Furthermore, because they are only placed on the ear, there is a great deal of space for any external noise to travel around them and into the ear canal. It is on very rare occasions that you actually find a top quality supra-aural earphone, because they are simply unable to provide the kind of noise cancellation that circumaural or in ear headphones provide. Supra-aural earphones are lightly manufactured and as such are usually marketed for customers who are not particularly focused on headphone quality, but mostly looking for basic functionality.
Take for instance, most desktop or video game headsets tend to be supra-aural. They are mostly preferred because they are light and as such are suitable for the long, extended hours they will be used. Additionally, in cases like these audio quality is not of great importance since it they are mostly used for spoken communication, where clarity is the focus and nothing else really matters.
When it comes to passive noise cancelling headphones, circumaural or around the ear headphones provide a significantly better noise cancellation quality. They are bigger in size and as such they include more noise reduction material. This in turn creates a far better buffer against outside noise- think beats headphones. Essentially this means that they are heavily packed with layers of high top quality high density foam,, or some other sound absorbing material. Admittedly, this then makes them a bit heavier than the average headphones, but since they completely block the ear off, they keep out up to 95% of outside noise. Well, this is assuming that the circumaural earphones you choose, fit your ears snugly. If they are either poorly designed or not the perfect fit then ambient noise will still be able to make its way in.