What is sound?

Last update: April 5th 2019

In order to start with mixing, you need to understand the basics of what sound is. Sort of, anyway. It helps…

Sounds Like A Good Vibration

So, when a sound is made, it generates vibrations which sends out pressure waves. The pressure waves are variations in the atmospheric pressure. A human ear is able to catch that and your brain translates it into sound. Pretty cool, huh? Funny enough, your whole body is able to catch sound and absorb it. I’m sure you all have felt that bass going through your stomach, while you’re at a concert. But that’s just a nice little side note. Back on topic now.

Sound Waves

Various sounds generate various shapes of waves or even combinations of shapes. Imagine you’re looking at the sea and you see the waves all going into one direction. That would be a good visualization of a simple sound wave.

However, you also know that with a little bit of wind the wave could change, like go into another direction. That too, is a good visualization of a more complex sound wave.

Visualizing sound as water waves is a good comparison to how sound waves travel through air. Sound travels with 344 meter per second and has the freedom to travel in all directions. That’s why if your hearing is damn good, you could pick up on what someone’s saying at the other end of the room.

Screenshot 2014-09-18 21.59.43


Every sound wave, of any kind, always has a frequency. The best example I once heard to describe this, is to imagine you have a bowl of water and you’re looking at it from the top. Suppose you stick an electric tooth brush in there and you turn it on. You’ll see the water ripple; waves will spread out to the side of the bowl. The higher the speed of your tooth brush, the higher the frequency of the ripples: meaning there are more waves of water moving from the center of the bowl to the edge per second. Sound can have a low frequency (not many waves) and a high frequency (many waves).


In order to create a sound wave, you need air molecules. Luckily, they are all around us. Air molecules will respond to the vibration a sound makes, and will then effect the atmospheric pressure. If you would to make a loud noise, the molecules will be pushed together real hard and they will be ripped apart real hard too, when the noise stops. This creates pressure waves in the atmosphere (the sound wave). The louder the sound, the bigger the change in pressure is. Therefore, a sound wave always has an amplitude, which is a sound pressure level (SPL) aka volume.


The measure used to describe the amplitude of a sound is decibel (dB). This shows the level of difference, between the sound pressure compared to the normal default pressure. When recording or mixing you’ll find out how important it is understand the importance of 0 dB.


The cool thing about recording digitally, is that the sound waves are turned into a visual presentation of lines, like you see when you play something on Soundcloud. It’s dense when there’s a lot of sounds coming together and thin when there are just a few sounds. When you have repetition in songs, you’ll also see a pattern. We can see that, but computers can too.

Clever people have already managed to program algorithms to determine patterns and compare them to other sound files. This has resulted in copyright checks, when you upload something to Soundcloud or YouTube, but it’s also used to research music. For instance, to discover how boring the 80s really were.

The reading of sound is also used for medical purposes. Many medical scans use sound to create photos, like echos.

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