All the Colors of Noise, Explained

This is going to be much more of a technically challenging article for me to write, but I’m going to give it my best shot because it seemed really interesting to investigate at the time.

There are two terms I should clarify before we get into the colors themselves: power and volume. Power describes the amount of energy that a wave has. As you increase a wave’s power, it also gains volume, essentially meaning that it just gets louder. Keep in mind that these two terms are related, but not necessarily equivalent.

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White noise

White noise is probably the term you’re most familiar with. It’s also one of the simplest ones to explain! To generate white noise, all you have to do is put an equal amount of power into every part of the spectrum. That’s why a graph of white noise looks so level—everything is roughly equal.

However, there’s a problem with white noise. Due to the way humans hear and process sound, white noise doesn’t actually sound equal at all frequencies to us. That’s where the difference between power and volume comes in. Even though white noise has equalized power everywhere, we perceive that is has more volume in the higher frequencies. There are a few ways to address that issue, some of which we’ll be discussing here.

Pink noise

Pink noise is one of the methods that gets closer to approximating human hearing. You can already tell from the graph, but pink noise works by gradually reducing the power of its signal as frequency increases. That leads to a gradually sloping-down graph, which fits our ears a little bit better. When you listen to the pink noise, you’ll notice that it’s missing much of the harsher, higher-pitched tones present in white noise.

Pink noise is often used to test audio systems. Because it sounds closer to the way we hear noises naturally, audio engineers can play pink noise and determine whether a speaker, microphone, or any audio device is recording or outputting noise properly.

Brown noise

Brown noise is, in many ways, the more extreme version of pink noise. As you can see, it puts a lot of emphasis on the lower frequencies, and drops off at about twice the rate of pink noise in the higher range.

It doesn’t have many official technological or scientific uses, but it is extremely popular among people who use noise generators to fall asleep. The specific frequencies that brown noise emits match with quite a few of the sounds that one might encounter in nature. When you listen to brown noise, imagine rain falling on a roof or the sound of a distant waterfall. Very relaxing, am I right?

Blue noise

Now we get into the ones that aren’t as fun to write about…or listen to. Blue noise is sort of like the inverse of pink noise—whereas pink noise decreases in power over its frequencies, blue noise gets more powerful as you go up.

It’s a harsh thing to listen to, but it does have some usefulness. If you’re in a loud situation, blue noise can actually be great at drowning out those sounds. It sounds paradoxical, but it does work! Additionally, blue noise is often used in “dithering” which is essentially the process of reducing distortion in audio or images.

Violet noise

Oh no! I’m not a fan of this one at all. Like before, violet noise is sort of the inverse of another spectrum we’ve seen already. This time, it’s brown. You can see how it puts a lot of power into the highest frequencies, while leaving practically nothing in the lower ones. When you listen to violet noise, you might imagine something like a running kitchen sink.

Surprisingly, violet noise does have some medical use. For many people with tinnitus (or ringing in the ears), violet noise can help to drown out the high-pitched noise they hear.

Gray noise

Gray noise is certainly the strangest of all the graphs we’ve seen so far. Before you listen to it, it’s difficult to imagine how gray noise might sound, but…it actually sounds pretty normal. And that’s by design!

Earlier, I mentioned that white noise had equal power at all frequencies, but not equal volume. Gray noise is the solution to that issue! Although it doesn’t have equal power at every frequency, we perceive it to have an equal volume at every frequency. That makes gray noise another of the more popular choices for people to relax with.

Esoteric colors

I’ve only just barely covered the most popular six colors of sound. If you do enough looking around online, you’ll be able to find many more variations and colors. I won’t go into all of these individually, but here are a few of the less well-known types of sound:

• Red noise

• Black noise

• Green noise

• Yellow noise

• Orange noise

Unfortunately, since there aren’t many conventions for what each of these terms mean, I can’t even give you a definite example of them! For now, you’ll just have to dive in for yourself and enjoy the world of weird noise.

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image credits: all six noise color visualizations were created by Warrakkk, are licensed under CC BY-SA 3.0, and are available to view and download at Wikimedia Commons. [white] [pink] [brown] [blue] [violet] [gray]
”Visual white noise, high definition LED TV, Wedgwood, Seattle, Washington, USA” by Wonderlane is licensed under CC BY 2.0.

sound credits: white and grey noises are in the public domain. the other four audio tracks were created by Omegatron, are licensed under CC BY-SA 3.0, and are available to view and download at Wikimedia Commons. [pink] [brown] [blue] [violet]