Do sounds have color? They do in science, and there’s practically a rainbow to fill your ears. Streaming white noise, which sounds like the fizziness of television static, has been shown help people study or go to sleep. And listening to pink noise, like the sound of waterfall, is being studied to see if it boosts cognitive performance.
But it’s brown noise that is all the rage right now on social media platforms and music apps. So, what exactly is brown noise and should you listen to it for long periods of time?
What Is Brown Noise?
Brown noise is one classification of noise “color.” Each color represents long-lasting patterns of noise frequencies that we can hear, ranging from 20 to 20,000 hertz.
“White noise has equal energy at all frequencies. To us, it sounds like radio static,” explains Anahita Mehta, a researcher who studies sound pitch at the Kresge Hearing Research Institute at the University of Michigan. “Pink noise has more energy in low frequency ranges compared to the high ranges. It sounds lower than white noise. Examples would be rainfall or traffic.”
Other noise colors include blue and violet, which have more energy in very high frequencies, like the sound of a snake hissing or steam leaking from a pipe.
Then, there’s brown noise. It’s technically classified as red noise, but the epithet comes from the way it’s produced: Its sound signals change randomly to produce the sound of static, mimicking a type of erratic movement pattern, called “Brownian motion,” named after Scottish botanist Robert Brown.
“Brown noise has even fewer high frequencies than white or pink noise, and you’ll recognize it as a lower sound,” Mehta says. “Examples would be the deep roar of an ocean wave crashing or thunder rolling.”
White Noise vs. Brown Noise
White noise has long been the most common color of noise you hear about, perhaps because the term has become a catchall phrase for any ambient noise — like fans, waves, thunderstorms or heartbeats — regardless of its color.
But brown noise made itself heard this past summer. It began trending on social media as people posted videos claiming it helped them focus, calm down or sleep.
The hashtag #brownnoise is now up to 95 million views on TikTok, and there’s a plethora of hours-long audio loops on YouTube, many of them with millions of views. You can also find curated brown noise playlists on Spotify and other music streaming platforms.
Brown Noise Benefits
Although brown noise is the latest trend to make its way onto social media, scientists can only speculate about its benefits. Very little evidence exists on the effect of brown noise, and the evidence that is available has included only small groups of participants for short periods of time.
But there’s a growing interest to see if brown noise might help health in the following ways:
There are many ways to elicit the relaxation response, the opposite of the fight-or-flight response that triggers stress. Well-established methods include deep breathing, meditation and guided imagery. Researchers suspect that brown noise may help elicit the relaxation response in some people.
“Maybe you find it relaxing to hear the sounds of the sea, so if you listen to brown noise that sounds like waves crashing, and it helps you, that’s great — as long as you’re listening at a low volume,” Mehta says. “However, there’s no strong evidence that listening to brown noise reduces stress.”
For experts, the jury is still out on the sleep benefits of white noise. In a September 2020 paper published in Sleep Medicine Reviews, Dr. Mathias Basner, a sleep researcher at the University of Pennsylvania Perelman School of Medicine, and his colleagues reviewed 38 studies that looked at the effect of continuous noise on sleep. They found only a mixed bag of low-quality studies and results that did not clearly provide evidence to support the idea that continuous white noise machines promote sleep.
However, he notes, the absence of evidence is not evidence of absence — meaning, even though there isn’t substantial evidence of the benefits of white noise on sleep at the moment, it doesn’t necessarily indicate that white noise doesn’t work either.
“It might mask other sounds, have a sleep-promoting quality that can lull people to sleep like a lullaby, or condition people so that the body knows it’s time to sleep,” Basner says.
Despite anecdotal testimonials on TikTok, there is no conclusive evidence that supports the theory that brown noise helps alleviate attention deficit hyperactivity disorder, but there have been small studies suggesting that white noise might offer some benefits to improve aspects of memory and academic performance in children with ADHD.
“The findings would need to be reproduced by other studies, but if it works for white noise, then theoretically, there’s no reason why it wouldn’t work for brown noise,” says Joel Nigg, director of the Oregon Health & Science University Center for ADHD Research in Portland, Oregon.
Why might brown noise help? One untested theory, Nigg says, is that it could strengthen the part of the brain that filters out extraneous information, called auditory masking. In other words, the brain might be able to muffle noises you don’t want to hear, while amplifying the noise you want to hear.
[READ: A Beginner’s Guide to Meditation]
Brown Noise Risks
Despite the suspected promise of brown noise, researchers are also concerned about its potential harms. Basner’s research found some studies pointing to the potential for hearing loss.
Not only can listening to continuous noise during sleep mask important sounds, such as a crying baby or a smoke alarm, and affect the quality or duration of your sleep, experts believe it may also contribute to hearing loss. After all, your ears need to rest, as well.
“The best time to do that is when you’re sleeping,” Basner says. “But if you have a noise machine, the auditory system is processing this all night long, and there may not be time to recuperate.”
You could be at an especially high risk for hearing loss if you listen to sounds with the volume cranked, which can cause damage to the ear’s delicate hearing structures.
In a November 2022 paper published in BMJ Global Health, researchers at the University of South Carolina found that people between the ages 12 to 34 were at high risk for hearing loss because they regularly exposed their ears to extremely loud sound volumes on their personal listening devices or at entertainment venues. The meta-analysis pooled data from 33 studies and evaluated hearing loss among more than 19,000 people from 2000 to 2021. The researchers estimate 23.8% and 48.2% of hearing loss was attributed to headphone use and loud venues, respectively, putting 1.35 billion young people around the world at risk for the inability to hear and in need of hearing aid devices.
“Unsafe listening practices are highly prevalent worldwide and may place over 1 billion young people at risk of hearing loss,” the researchers wrote. “There is an urgent need to prioritize policy focused on safe listening.”
What You Should Do
Researchers are continuing to investigate the health benefits of noise machines, but it could be years before there is enough data to support or disprove claims. In the meantime, if you want to give it a try, experts don’t see a big risk to listening to white, pink or brown noise as long as you practice safe listening habits.
Here are a few helpful tips to get started:
— Listen only for brief periods, such as 10 or 20 minutes. If you’re using brown noise at bedtime, put the noise on a timer to give your ears a chance to recuperate once you’ve fallen asleep.
— Keep the volume low.
— Talk to your doctor if you have any questions or concerns about it.
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Clarification 11/18/22: A previous version of this article was not clear that researchers are still studying the potential effects of pink noise on cognitive performance and did not specify that one of the studies looked at continuous white noise.