What Is White Noise?

Every sound you hear is made up of sound waves. Every sound wave has a pitch, or frequency, that determines how “high” or “low” it sounds. White noise is the combination of many different frequencies, all equally loud.

White noise static on a TV screen — The “static TV” sound is an example of white noise.

White noise sounds like a “hissing” or “wooshing” sound. A well-known example of white noise is the “static” sound made by a radio or TV when it’s not receiving a signal. Most people also consider the sounds of ocean waves, rain drops, and even the gentle hum in an airplane cabin to be white noise, since those sounds cover a broad range of frequencies too.

What Is White Noise Used For?

Because white noise is composed of many different frequencies, it’s very effective for masking other sounds. Many people use white noise to drown out other noise while they sleep, study, while at work, or simply listen to clear their mind. Some use an electric fan to generate white noise to mask their noisy neighborhood while they sleep.

In the past few decades, psychologists have discovered listening to white noise has positive effects on memory and sleep. Their studies have shown white noise can help both babies and adults fall asleep faster, and have better quality sleep. Other experiments have shown white noise increases activity in brain areas related to motivation and cognition, and may improve memory in students with ADHD (attention deficit hyperactivity disorder).

Why Is It Called “White Noise?”

Both sound and light are made up of waves. Every wave of both types has a frequency:

Sound waves with different frequencies create different pitches. Low frequency sound waves make low pitches, and high ones make high pitches.

Light with different frequencies create different colors. The lowest frequency light we can see is red, and the highest is violet. The rest of the visible colors fall in between.

If you combine every frequency (color) of visible light at equal intensity, the light would look white.* Scientists named it white noise because it’s composed of many different frequencies of sound, just like white light is composed of all frequencies of light that we can see.

White Noise vs. “True” White Noise

“White noise” is a fairly loose term. In addition to the “static TV” type of white noise, the vast majority of people refer to the sound of rushing waterfalls, rain drops, ocean waves, etc. as white noise.

Scientists and engineers have a very specific definition for what they consider white noise though. To them, white noise is every frequency in a range at equal volume (what they call “flat spectral density”). “True” white noise can only be created with a computer or electronically. And this is what it sounds like:

True White Noise Player

You might notice it’s pretty difficult to listen to. The loud, higher frequencies are very harsh on the human ear.

Compare this to the sound of a peaceful rain shower:

The rain drops are probably more bearable.

“Natural” white noise sounds like these cover a broad range of frequencies, but unlike “true” white noise, the harsh high frequencies are usually quiet. Outside of science and engineering, the distinction between white noise and “true” white noise rarely matters. Practically speaking, nobody listens to true white noise for sleeping, concentration, etc. simply because it’s too hard to listen to!

When Was the Term “White Noise” First Used?

Thomas Edison with phonograph — White noise came about some time after Thomas Edison invented the phonograph in 1877.

The term “white noise” came into use some time after electronic sounds were first generated—after the phonograph and telephone in the 1870s. It’s unclear exactly when the term was adopted, but it gained use in the scientific community in the 1910s when white noise was used to mask other sounds in studies. As electronics and computing arose, the term became used more frequently in physics and engineering in the 1930s and 40s.

What Is Pink Noise?

As the name “white noise” might suggest, there are other “colors” of noise other than white noise. We discovered earlier in this post that “true” white noise is really harsh to most peoples’ ears, especially at high volumes:

True White Noise Player

Although all the frequencies are equally loud when they come out of a speaker, the human ear perceives higher frequencies to be louder than they actually are. This is why true white noise sounds so grating. Other “colors” of noise are also composed of a wide range of frequencies, but unlike white noise, the frequencies aren’t all equally loud.

To demonstrate, let’s take our “true” white noise example and try to make it more comfortable to the human ear. There’s a simple fix: make all those harsh high frequencies quieter, and the low frequencies louder. This is what sounds like:

It’s a little easier on your ears, right?

Keeping with the white light / white noise analogy, if you were to imagine this as light instead of sound, we started with white light, then turned up the low frequency red light, and turned down the high frequency blue and violet light. The resulting light would look pink-ish, which is why this is called pink noise.

What Is Brown Noise?

If we take our pink noise example and crank up the low frequencies and turn down the high frequencies even more, we get something like this:

Brown Noise Player

As you might expect, it sounds a bit deeper than pink noise.

If we again imagined this as light instead of sound, we just turned up the low “red” frequencies and turned down the high blue and violet frequencies even more. The resulting light would look red. You might have guessed that this should be called “red noise”—you would be correct, except it’s confusingly called brown noise, and even worse, it has nothing to do with the color brown.

Brown noise took its name from a term in physics: Brownian motion, which describes the random motion of particles, similar to the “randomness” of the noise. (And Brownian motion is named for Robert Brown, a 19th century botanist.) It’s not wrong to call this red noise, but brown noise is the far more common term.

In truth, most people who listen to “white noise” to relax, sleep, or mask noises are usually playing some form of pink noise, brown noise or a natural white noise such as rain or waterfall sounds, since they all lack those harsh high frequencies. It’s also common to see brown noise, pink noise, and natural white noise lumped together under the label of “white noise.” Outside of the scientific community, very few people make a distinction between them all (us included).

Are There Are Other Colors of Noise?

There are more colors beyond white, pink, and brown noise, but most are not comfortable to listen to. For example, blue and violet noise have really loud high frequencies—which we intentionally turned down in our pink and brown noise examples because they’re so harsh to listen to.

If you’d like to inflict some self-torture, here’s what they sound like:

Blue / Azure Noise Player

Violet / Purple Noise Player

They are even harder on the human ear than true white noise.

White Noise Benefits

Woman sleeping in a bed — Research shows white noise can improve sleep.

In the last few decades, psychologists have conducted a number of studies on the effects of white noise. Their research indicates listening to white noise may have a positive impact in two major areas of human behavior: memory and sleep.

In 2007, Swedish psychologists studied students with ADHD, and found the students had a much better ability to remember words later on if they listened to white noise while memorizing them.

A 2010 study by the same group showed similar results in inattentive children who listened to white noise while memorizing words.

And sleep studies have shown that listening to white or pink noise can help you fall asleep faster, and get better quality sleep:

In a 1990 study, researchers found 80% of babies fell asleep within five minutes while listening to white noise, compared to only 25% who didn’t.

A study published in Journal of Caring Sciences found that hospital patients who slept with white noise on had better and longer sleep than patients who did not.

Adults that listened to pink noise fell asleep 56% faster in a 1993 experiment.

In an experiment published in Frontiers in Neurology, insomniacs who were exposed to broadband sound (white noise is a type of broadband sound) fell asleep 38% faster, and experienced better quality sleep.

One study on older adults showed that listening to pink noise while you sleep may even improve your memory!

White Noise, Pink Noise, Brown Noise, Natural White Noise… Which Is Best?

There’s no right or wrong answer when it comes to which you should listen to, as long as you play them at a reasonable volume. Choose whichever sound makes you feel most comfortable!

Ready to relax?
Listen to Zenibly’s white noise on Apple Music and Spotify!

*At the time, it was assumed that every color that makes up white light has equal intensity, but in reality this isn’t true. For example, sunlight has more green light than violet and red. Light bulbs don’t have equal color intensity either.