Ambient noise is the enemy to all headphones; we’re always looking for the best noise cancelling headphones to drown out our busy lives and focus on what we are watching or working on. In a busy office space, or even a busy home, concentrating on your work is a paramount priority. (And if you’re traveling on an airplane or a train, a little extra silence can be golden.) For someone like me, whose office is anywhere I can get an Internet connection, it can be hard at times to concentrate on work. If you share my situation, you might be in the market for buying noise cancelling headphones; knowing all you can about them before you plunk down any cash (they can be expensive) is advised. One popular question that is asked about these devices is exactly how the headphones drown out the outside noise. These exact methods are patented, but we can give you the gist of how they work.
As an amateur audiophile, I know a thing or two about how these noise cancelling headphones work. One of the most popular noise cancelling brands is Bose. It’s been a sort of standard in noise cancelling technology with headphones and audio products.
If you want to understand noise cancelling technology, you have to think of waves — not water waves, but audio waves. If you don’t know how audio works, think of how waves go up and down, and are spread out in different lengths. Sound waves are almost the same as water waves, but audio waves are longitudinal. These waves are created by a mechanical vibration that produces compressions and refractions. In turn, these compressions and refractions produce the sound.
To understand the process of noise cancelling, we must first understand a couple of elements found in audio waves. First, there is the crest, which is the top of each wave. Second, we have the wavelength, which is the distance between the top of each crest. Next, we have amplitude, which is how high the peak goes from the level point of the wave. Last, we have trough, which is the opposite of the crest and is the lowest point.
Now that you’ve grasped an understanding of how audio works, let’s take a look at how headphones utilize this technology to produce the sound. Headphones have small diaphragms that are made of paper, metal, or plastic and surrounded with electrodes. When an electrical signal is run through the lines, it makes the material push and pull. By varying the signal, the diaphragm makes the pushing and pulling vary in speed, and this variation in pushing and pulling creates the sound. All types of headphones — from in-ear, on-ear, and around-ear — use this basic method.
Now that we know how your ears receive the sound, we can get into the meat of the matter: how noise cancellation works. There are two type of cancellation: active and passive. Passive noise cancellation is pretty simple. Headphones that use this method are usually packed with high-density foam and are designed to keep the sound of the headphones feeding into your ears while the foam acts as a barrier between your ears and the sound to which you’re listening. Passive noise cancellation headphones are on the low-end of the price spectrum and provide adequate noise cancelling. On the higher end of the price spectrum, we have active noise cancelling, which will cost you more money but provide a better shield between you and the outside world. Among the most popular active noise cancelling headphones are the ones made by Bose. Active noise cancelling headphones do everything that passive ones do, but have the added ability to actively silence low-end sounds.
Active noise cancelling headphones make their own sound waves to battle the ones trying to destroy your audio experience. They usually require a battery to be powered and the process by which these sound waves are created can be complicated. The simple way of explaining this is that the active noise cancelling headphones will recreate the wavelength trying to enter the headphones and output the wavelength in the direction of the obstructive noise. When both of these sound waves hit each other, they dissipate thanks to the intervening void that’s created.
Active noise cancelling headphones have their own elements that help block out sound. They include microphones, their own circuitry, dedicated speakers for each side of the headphones, and a battery. All of these elements are dedicated to analyzing and counteracting the ambient noise. With technology like this, the headphones are able to reduce about 20 decibels of sound, meaning that about 70% of any incoming noise is blocked from entering your ears. This is the basic technology behind Bose headphones and others like them.
It’s a common complaint by users that, while these headphones are great for cancelling out unwanted noises, they lose the ability to properly recreate both the ultra-high and ultra-low sounds that are needed for most audio producers trying to do audio checks or productions. Although the people who I talk with say that, even for the downside of the loss of two ends of the spectrum, they would never go back to regular headphones again because of the advantages of the sound isolation inside of noise cancelling headphones.