What’s the Difference Between White, Red, Grey, and Pink Noise?

What’s the Difference Between White, Red, Grey, and Pink Noise?

A recent article in the Smithsonian Online Magazine stated that “Pink Noise May Improve Sleep and Memory in Older Adults”.  The idea being that pink noise may lull adults into a deeper sleep, thus improving their sleep to begin with, and later on, improving their memory.  If you’re interested in this research, you can find the Smithsonian article here, or alternatively, the TIME magazine article on the same subject here.

But this begs a question:


What’s the Difference Between All These Colored Noises?

In actuality, there’s quite a few different colored noises.  The most common of these noises is “white noise”, which also has been stated to improve memory and sleep. According to the National Sleep Foundation, “White noise works by reducing the difference between background sounds and a “peak” sound, like a door slamming, giving you a better chance to sleep through it undisturbed. […] If you have difficulty falling asleep or staying asleep, creating a constant ambient sound could help mask activity from inside and outside the house”.

When white noise was (for a lack of a better term) “discovered”, it began the trend of naming colors after noises. These names aren’t for nothing, either. Different color noises have different properties, and they vary drastically.

White noise is defined by Merriam-Webster as: “a heterogeneous mixture of sound waves extending over a wide frequency range”.  In other words, according to Brain Stuff on YouTube, “white noise is the noise produced by combining all the different frequencies of sound together at once”.  White noise has an equal amount of noise distribution throughout, and that’s where the differences in colored noises really begins to show up.

For instance, Pink noise is defined as: “a mixture of sound waves with an intensity that diminishes proportionally with frequency to yield approximately equal energy per octave”.  In other words, the “power per hertz in pink noise decreases as the frequency increases“.

pink noise
A visual representation of white noise vs pink noise as brought to you by The Atlantic and The Physics Hypertextbook

Red noise (otherwise named Brownian noise thanks to scientist Robert Brown) is what it may sound like to you. Since red is a deeper shade of pink for all practical purposes, red noise is basically a deeper pink noise.

In addition, Grey noise is similar to white noise, but there is a key difference. That difference being that while white noise has frequencies of equal energy, grey noise has frequencies of equal loudness. There’s not really a true “grey noise”, in actuality.


Can These Noises Actually Help Us Sleep and Improve Memory?

As mentioned before, white noise works by blocking out sudden noises by giving the user one continuous sound to listen throughout the night. In that sense, yes, it can help you sleep, and it has even been suggested that it can help you focus on studying or work tasks.  (I have personally found that it’s useful for when I’m reading — it seems to keep my mind from wandering — though this is not based on a scientific study, just personal experience.)

Pink noise, on the other hand, does seem to work the same way.

From the aforementioned Smithsonian Article: “The results of the study, published in the journal Frontiers in Human Neuroscience, found that participants’ slow waves increased after the night of sound stimulation, suggesting that they were getting more deep sleep. And on the morning after hearing pink noise, they performed three times better on memory tests than they did after sleeping without any sound stimulation.”

However, the article also noted that more research needs to be done before this is stated as fact as the study conducted was relatively small in size.

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