(Intro)

When we think about colors, we normally connect them with light - things you can see like white clouds, pink flowers, and brown cows. But color can also be used to describe some special sounds: white, pink, and brown noise.

They're very specific types of the kind of noise you'd probably think of as static, designed to sound a certain way based on the physiology of human hearing. And because of human evolution, they can also be useful for when you're trying to concentrate. Have a listen to this. (White noise plays) This is white noise.

Both light and sound are made of waves, the frequency of the waves - how quickly they vibrate - are important in how we perceive them. You might know that white light is made up of light of all different colors of the rainbow, all frequencies we can see. White noise gets its name because it contains sounds from all across the frequencies we can hear.

That's a big range, from around twenty to twenty thousand Hertz, or wave vibrations per second. These frequencies are played in fast random succession and your brain combines these random fast changing frequencies into a fuzzy hiss of static.

Now, you may have noticed that the white noise sounds kind of high pitched, which seems weird. If white noise is made up of sounds with totally random frequencies, you'd think it would sound sort of middle pitched.

The reason white noise sounds high pitched has to do with your biology, the way your ears and brain detect and process sound. What you hear as pitch isn't quite the same as the objective frequencies produced and detected by machines.

Your hearing system and music is based on octaves. When you play a string of notes, each one octave apart, like a row of Cs, it might sound like they are evenly spaced in terms of how high they are. That's not actually the case.

Instead, each octave represents a doubling in frequency, meaning there are twice as many possible frequencies for our random sampler to choose from, so in a random set of frequencies, statistically more of the sounds will seem higher pitched to the human ear.

And there's another reason white noise sounds high pitched. Human anatomy makes us more attuned to sounds in the highest region of three to four kilohertz.

Our brains amplify sounds in this higher pitched region, making the higher frequency sounds in the white noise seem louder than they really are.

So if you find white noise (White noise plays) a bit too tinny, you might prefer other colored sounds, like pink noise (Pink noise plays)

Pink noise takes human hearing into account and balances out the frequencies so that all octaves are represented evenly. In pink noise, the frequencies played are still random, but the volume of the higher frequencies is dampened.

The higher the frequency, the more the volume is lowered, which compensates for how often the higher sounds are played. To your ears, the different pitches come through equally strong and the result is a deeper, more balanced listening experience.

Brown noise takes this idea a step further, sapping even more volume from the higher frequencies. This creates a more bassy rumble, like this (Brown noise plays) which sounds a bit like a large waterfall or distant traffic.

Now if you just glanced worriedly down at your pants, you've probably heard about the infamous Brown Note. Supposedly, there's a particular tone that's too low for humans to hear but apparently vibrates through your body, including your bowels, causing involuntary motions down there.

Do not worry though, you and your rear end can rest assured, this myth has been well and truly busted. You're safe to enjoy brown noise without any additional brown.

There are other noise colors too, with frequencies that are adjusted in different ways, but white, pink, and brown are the three main ones.

You might find the sounds of white, pink, and brown noise relaxing and if you do, you're not alone. Many people play these sounds to help them work or sleep - but why? Again, the answer lies in human biology.

Your brain is especially attuned to detect changes in your surroundings if there's a low level of background information. Like, it's easy to tell the difference between two and three people talking at once compared to ninety-nine versus a hundred people chatting away. Still just one extra person, but your brain has a harder time detecting that.

When it's silent, almost any sound can alert your brain and you can't help but pay attention. After all, it might signal danger, a throwback to our evolutionary ancestors' worries about predators or other threats.

An unfortunate side affect is that a dripping tap or snoring partner in a quiet room can lead to some pretty frazzled nerves.

But white, pink, and brown noise - playing across all frequencies - are like muffling blankets of sound, they mask other sounds by making them less significant compared to the background.

So the solution to annoying noises can sometimes be more noise, sounds that come in many colors.

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