If you love the sound of thunder or crashing waves, brown noise may help you focus or get to sleep

• Brown noise has a low, natural sound, so many people find it easier on the ear than white noise.
• Examples of brown noise include rushing waterfalls or rivers, heavy rainfall, and rumbling thunder.

You might already be familiar with white noise, if you prefer the sound of a whirring fan to block out distractions at work. Maybe you even use pink noise, like the gentle crash of ocean waves against the shore, to get to sleep.

But there's another frequency to try: brown noise, also called Brownian noise or red noise, which emphasizes lower-frequency sounds. It has the deepest intensity of all noises and sounds like a low roar or rumbling.

Here's what to know about brown noise and how it could help improve your concentration and focus.

Brown noise vs. other noise types

It might sound strange to think of noises as having "colors," but the color of a certain noise is based on its frequency.

In fact, they were named based on the order of colors in a rainbow. Like the lowest frequencies of visible light, the lowest frequencies of sound are red — they're just usually called "brown" because they closely resemble Brownian motion. The highest frequencies of sound are violet.

White noise lies smack in the middle, with an equal volume of all frequencies, but it's not a sound you'll find in nature. White noises are usually man-made and familiar, like radio static, a whirring fan, or humming AC units.

Like white noise, brown noise contains all frequencies. But it places a larger emphasis on lower frequencies, so higher pitched sounds are quieter and low tones are louder.

Brown noise sounds a little less "'sharp" than white noise because it has rounder, more soothing characteristics, says Dr. Amy Sarow, clinical audiologist at Michigan Ear Institute.

Examples of brown noise include:

• Thunder
• Crashing waves
• Heavy rain
• Strong waterfalls
• A shower

Other kinds of noise:

• Pink noise falls between white and red (brown) noise. It places a larger emphasis on high frequencies than brown noise, but less than white noise. You'll find plenty of examples of pink noise in nature, like wind blowing through trees, low waves, or steady rainfall.
• Blue noise has high frequencies that come in a little louder than low frequencies. It sounds something like a hissing water spray.
• Violet, or purple noise is the exact opposite of brown noise, with louder high frequencies than low frequencies. Violet noise sounds something like high-pitched TV static.

What are the benefits of brown noise?

Brown noise may sound a little "rougher" than other noises, but it can still have a calming effect.

• It could help lull you to sleep: Rhythmic brown noises like crashing waves and heavy rain may help lower your heart rate and calm your breathing so sleep comes more easily.
• It can aid your concentration and focus. Brown noise may have a positive impact on your working memory because it increases the firing rate of neurons in your brain. This promotes quicker access to stored information, Sarow says. In theory, it may help improve attention span, which could have benefits for people living with ADHD.
• It can help cut down on distractions. Using a brown noise machine is a great way to drown out distracting noises so you can focus while working, says Andrew Kahn, licensed psychologist and Senior Subject Matter Expert at Understood.org.
• It can help promote relaxation. The sound of ocean waves, for example, may reduce stress and help create a calm environment. The rhythmic sound of rain may also help relax your brain.
• It may help mask tinnitus. Many people with tinnitus, a condition that causes a constant ringing in your ears, prefer the "softer" sounds of brown noise over the sharper frequencies found in white noise, Sarow says. Depending on the severity of your tinnitus, brown noise may reduce the ringing, or eliminate it altogether.

Where can you find brown noise?

You no longer need to purchase a CD or sound machine to play soothing sounds as you fall asleep at night — though of course you can, if you prefer. You'll find plenty of free playlists on YouTube and elsewhere across the internet. You can also use your phone or other device to download sound apps.

Apps to try include:

• Calm
• BetterSleep
• Sleep Sounds

Headphones or speakers?

In a noisy environment, headphones can help minimize distractions and improve your focus when studying and working. But if you need help stimulating your brain while working at home and don't want to wear headphones all day, you might prefer to use speakers rather than wear headphones for several hours in a row.

Since brown noise doesn't fluctuate in pitch like regular music, try to keep the sound no louder than speaking volume, especially if you plan to listen to it throughout the day.

If you can still hear the sound when you hold your headphones at arm's length, you might want to consider turning it down. Since speakers don't play directly into your eardrums, you can get away with a slightly higher volume.

When it comes to tinnitus, feel free to use either headphones or speakers — with tinnitus, what matters most is suppressing the ringing in your ears. Sometimes all it takes is a bit of constant background noise, but if your tinnitus persists, headphones may do a better job of keeping the ringing at bay than speakers.

Insider's takeaway

Research on brown noise remains limited, but existing evidence suggests it may have potential to help improve focus, concentration, and sleep — especially if you live with ADHD.

Ocean waves, waterfalls, and thunder are just a few examples of soothing brown noise sounds, but if those aren't your jam, you can also try listening to straight static frequencies.

Many apps and internet playlists even let you mix and match different sounds and frequency strengths to make a unique sound that works for you.