Brown noise (also called Brownian noise or red noise) is a type of broadband sound that contains every frequency the human ear can hear, but with far more energy in the low frequencies than the high ones. Technically, its power spectral density is proportional to 1/f² and falls by about 6.02 dB per octave as frequency rises, which is twice the roll-off of pink noise. Because the highs are so suppressed, it loses the harsh "hiss" of white noise and instead sounds like a deep, soft rumble — a steady waterfall, heavy rainfall, or distant thunder. The name comes from Robert Brown and Brownian motion (the random-walk process that produces this exact slope), not from the color, per Wikipedia's entry on Brownian noise.

What does brown noise do, and what is it good for?

Brown noise is used for three main things: masking distracting sounds, helping people fall asleep, and supporting focus or concentration. The mechanism is masking — a steady, low, predictable wash of sound makes intermittent noises (traffic, a noisy office, a partner snoring, tinnitus ringing) less noticeable, so they're less likely to pull your attention or wake you. There's reasonable evidence that this kind of broadband masking helps some sleepers: one randomized crossover trial found broadband sound cut the time to fall asleep by about 38% in healthy young adults. But the evidence for brown noise specifically — versus white or pink noise — is limited, and much of the focus/ADHD benefit is anecdotal rather than proven.

Does brown noise help with ADHD and focus?

A lot of people with ADHD report that brown noise helps them concentrate, and it went viral on social media for exactly this. But the science is thinner than the hype. The Attention Deficit Disorder Association (ADDA) is explicit that the benefits of brown noise "are mainly based on anecdotal evidence" and that there is currently "a lack of research proving the benefits of brown noise." The research that does exist is mostly on white noise: a 2007 study in the Journal of Child Psychology and Psychiatry found moderate auditory white noise improved cognitive performance in children with ADHD while slightly worsening it in typically-developing peers — an effect researchers attribute to "stochastic resonance." That's promising and plausibly extends to brown noise, but it isn't a study of brown noise. Bottom line: if it helps you, use it — it's low-risk — but treat "brown noise fixes ADHD" as an unproven claim, not a fact.

Is brown noise safe, or can it be harmful?

Brown noise itself is not harmful — the only real risk is the same risk as any audio: listening too loud for too long. Hearing damage is a function of volume and duration. NIOSH sets a recommended exposure limit of 85 A-weighted decibels (dBA) averaged over an 8-hour day, and for every 3 dBA louder, safe exposure time roughly halves. So the practical safety rule is to keep brown noise at a comfortable, conversational-or-lower level, not cranked. The Cleveland Clinic specifically suggests keeping sessions to about 10–15 minutes at a lower volume and using a sleep timer rather than running it loudly all night, to give your ears a chance to recover. Used at sensible volumes, it's safe for daily use.

What's the difference between brown noise and white noise?

All three common "colors" are broadband sound; the difference is the tilt of their frequency balance. White noise has equal energy across all frequencies — a bright, full "shhh" like untuned radio static or a fan. Pink noise rolls off the highs by about 3.01 dB per octave (energy proportional to 1/f), so it sounds more balanced and natural, like steady rain. Brown noise rolls off twice as steeply, about 6.02 dB per octave (energy proportional to 1/f²), pushing nearly all the energy into the low end — a deep rumble like a waterfall or distant thunder. People who find white noise too harsh often prefer brown noise's softer, bassier character. For the full comparison, see our brown noise vs white noise guide.

How loud and how long should I listen to brown noise?

Keep it comfortable and don't run it loud for hours. A good rule of thumb is to stay well under 85 dBA — the level NIOSH treats as the start of the hazardous range over a full day — and to use the lowest volume that still masks whatever you're trying to drown out; louder isn't better for masking. For sleep, the Cleveland Clinic suggests a sleep timer and lower volume so the sound isn't blasting in your ears all night. For focus, listen for as long as it's useful, but if you ever notice ear fatigue or ringing, that's the signal to turn it down or take a break. There's no benefit to maxing the volume — masking works at modest levels.

What Is Brown Noise? (Benefits, Safety & How to Use It)

Brown noise — also called Brownian noise or red noise — is a broadband sound with its energy concentrated in the low frequencies, so it sounds like a deep, soft rumble: a steady waterfall, heavy rainfall, or distant thunder. Spectrally, its power falls by about 6.02 dB per octave as pitch rises (its density is proportional to 1/f²), which is twice the roll-off of pink noise and the opposite of white noise's bright hiss (Wikipedia: Brownian noise). People use it to fall asleep, block distractions, and focus — and it's become especially popular in the ADHD community.

Here's the honest version of what it is and what it does, with the evidence — and the gaps in that evidence — laid out plainly. If you searched what is brown noise after a video told you it would fix your focus, this covers the definition, the real benefits, the safety question, and how it compares to white noise.

What Brown Noise Actually Is

Every "color" of noise is broadband — it contains many frequencies at once. What separates them is the balance: how the energy is spread across low, mid, and high frequencies. That balance is the "color."

Brown noise is the one tilted hardest toward the bass. Per Wikipedia's entry on Brownian noise, its spectral density is "inversely proportional to f²" and it "decreases in intensity by 6 dB per octave (20 dB per decade)." In plain terms: every time the pitch doubles, the power drops to about a quarter. So the low rumble dominates and the highs are heavily suppressed — which is exactly why brown noise loses the harsh top-end "shhh" of white noise and instead sounds, in Wikipedia's words, like "a low roar resembling a waterfall, heavy rainfall, or the distant rumble of thunder."

A couple of things people usually get wrong:

The name has nothing to do with the color. It's named after Robert Brown, the botanist who described Brownian motion — the random, erratic "random walk" of particles in a fluid. That random-walk process mathematically produces this exact 1/f² slope, which is why the sound is called Brownian noise. It's also called red noise by analogy with light, since the energy piles up at the low (long-wavelength, "red") end.
It's not just "bass-boosted white noise" by feel — it's a defined slope. White, pink, and brown are precise mathematical recipes, not vibes.

Brown vs. White vs. Pink, in One Table

You don't need the deep theory to choose — you mostly need to know how each one sounds and how steeply it rolls off. Here's the one-line version (the pillar guide goes deeper):

Color	Spectral roll-off	Energy ∝	Sounds like
White	flat (equal power per Hz)	constant	Bright, full "shhh" — untuned radio static, a fan
Pink	−3.01 dB / octave	1/f	Balanced, natural — steady rain, rustling leaves
Brown	−6.02 dB / octave	1/f²	Deep rumble — waterfall, heavy rain, distant thunder

Those figures are from Wikipedia's "Colors of noise": white noise has "equal power in any band of a given bandwidth," pink "decreases by 3.01 dB per octave," and brown "decreases 6.02 dB per octave." The practical takeaway: if white noise feels too sharp or hissy, brown noise is the softer, bassier alternative — same masking idea, gentler on the ears. For the full head-to-head, including which to pick for what, read brown noise vs white noise, or start with the basics in what is white noise.

What Brown Noise Is Good For — and What the Evidence Says

This is where it pays to separate what's well-supported from what's popular but thin. Brown noise gets credited with three things: sleep, focus, and relief from tinnitus or a noisy environment. The honest evidence picture differs for each.

Sleep: the strongest case (but it's about masking)

The mechanism here is masking — a steady, predictable wash of low-frequency sound makes sudden noises (a slamming door, traffic, a snoring partner) blend into the background, so they're less likely to jolt you awake or keep you from drifting off. The Sleep Foundation frames it this way: researchers are "hopeful that the steady hum of white noise might reduce a sleeper's sensitivity to unpredictable noises from the environment."

There's real experimental support for broadband masking helping sleep onset. A randomized crossover trial published in Frontiers in Neurology, "Broadband Sound Administration Improves Sleep Onset Latency in Healthy Subjects in a Model of Transient Insomnia", found that broadband sound cut the median time to fall asleep by about 38% — from 19 minutes down to 13 minutes (p = 0.011). Worth being precise about the limits the authors themselves flag: it was a small study (18 healthy young adults, not chronic-insomnia patients), the broadband sound was only about 6 dB above the quiet control (46.0 vs 40.1 dB), and they note "further study is needed to determine effectiveness in patients complaining of insomnia."

Two honest caveats sit alongside that result. First, this is broadband noise, not brown noise specifically — the colors haven't been cleanly head-to-head tested for sleep. Second, masking isn't universally beneficial: the Sleep Foundation points to a systematic review that "call[s] into question the quality of existing evidence" and warns that "in some instances, white noise can disturb a person's sleep and may affect their hearing." So: helpful for many people, especially light sleepers in noisy environments — but not a proven cure, and not for everyone.

Focus and ADHD: popular, but the evidence is thin

This is the use that made brown noise go viral, and it's where the gap between hype and proof is widest. People — especially people with ADHD — report that the low rumble quiets mental chatter and helps them lock in.

But the brown-noise-specific science barely exists. The Attention Deficit Disorder Association (ADDA) says it directly: the benefits "are mainly based on anecdotal evidence," and "currently, there is a lack of research proving the benefits of brown noise." The research that does exist is mostly on white noise. A frequently-cited 2007 study, "Listen to the noise: noise is beneficial for cognitive performance in ADHD" (Journal of Child Psychology and Psychiatry), found that moderate auditory white noise improved cognitive performance in children with ADHD while slightly worsening it in typically-developing children — an effect the authors attribute to stochastic resonance (the idea that the right amount of noise can nudge an under-aroused system toward better signal processing). That's a genuinely interesting result, and it's plausible the same idea extends to brown noise — but it is a study of white noise, not brown.

So the accurate framing is: brown noise for focus is low-risk and widely liked, but not scientifically proven. If it helps you concentrate, that's a real, usable benefit — just don't mistake the popularity for settled evidence.

Tinnitus and noisy environments

The masking logic applies here too. The Cleveland Clinic notes brown noise "might also be helpful… for anyone who has tinnitus" by helping to "block out loud or disruptive noises." It can make ringing or an irritating ambient hum less prominent. As with sleep, this is symptom masking, not treatment — but for a lot of people, masking is exactly what they want.

Is Brown Noise Safe? The Honest Answer

Yes — at sensible volumes. Brown noise is not inherently harmful; the only real risk is the one shared by all audio: listening too loud, for too long. Hearing damage is a function of loudness × duration, not of which color of noise you play.

The reference point worth knowing comes from CDC/NIOSH: the recommended exposure limit is 85 A-weighted decibels (dBA) averaged over an 8-hour workday, and "for each 3 dBA increase in noise level, NIOSH recommends reducing the exposure duration by half." That exchange rate is the key intuition — louder sound is safe for much less time. The practical rule for brown noise: keep it comfortable and low, well under that 85 dBA threshold, and use the quietest level that still masks what you're trying to drown out. Louder does not mask better.

For sleep specifically, the Cleveland Clinic — quoting child and adolescent psychiatrist Shivnaveen Bains, MD — recommends listening "for brief periods of 10 to 15 minutes at a time," keeping the volume "at a lower volume," and using "a timer to give your ears a chance to recover before you fall asleep" rather than "listening to them all night long." One more reason not to crank it: the Sleep Foundation notes that a large share of consumer white-noise devices tested could reach dangerously loud levels, so device defaults aren't a safe-volume guarantee — you set the level.

The same Cleveland Clinic piece is refreshingly candid about the limits of the science overall: for brown noise, "the benefits are still under research, and that research is minimal," and "it's too soon to tell just how helpful it can be." That's the right posture — try it, keep it quiet, and judge it by whether it helps you.

How to Use Brown Noise (and Where to Play It Free)

A few simple guidelines that follow from everything above:

Pick the volume by masking, not by maximum. Turn it up just until the distraction fades, then stop. That keeps you safely under hearing-risk levels and works better anyway.
Use a timer for sleep. Mask your way into sleep, then let it stop — per the Cleveland Clinic's 10–15-minute, lower-volume, timer-based suggestion.
If white noise felt harsh, brown is the gentler swap. The −6.02 dB/octave roll-off is why it sounds like a soft rumble instead of a hiss.
Treat the focus/ADHD benefit as personal, not proven. It's low-risk; let your own experience be the test.

You can try it right now, free, with no sign-up on HowWorks Sound. The brown-noise Focus scene is a continuous, low-rumble wash built for working and studying; the brown-noise sleep mix runs deeper and calmer for winding down. Press play and it just runs — no ads, no account.

If you want the bigger picture, the pillar guide brown noise vs white noise compares all the colors and helps you choose, and what is white noise covers the brighter cousin. Curious about other focus-audio claims? See whether binaural beats actually work and the honest take on whether music helps you focus.

Brown noise is a simple, well-defined thing — low-frequency broadband sound that rumbles instead of hisses — wrapped in more certainty than the science yet supports. Now you know what it really is, what it's genuinely good for, and how to use it safely.

▶ Play brown noise free on HowWorks Sound — no sign-up — or sink into the deeper sleep mix.