White, pink and brown noise are all steady, random "shhh" sounds that cover the whole range of frequencies. The difference is how the power is spread: white noise has equal power at every frequency and sounds like a bright hiss, pink noise gets softer toward the high end and sounds rounder, often compared to a waterfall, and brown noise drops off even faster and sounds like a deep, distant rumble. For sleep, research has not found a winner, so the best choice is the one you notice least at a low volume.
White, pink and brown noise at a glance
| Power spectrum | In decibels per octave | Sounds like | Often chosen for | |
|---|---|---|---|---|
| White noise | Flat: equal power at every frequency | 0 dB, flat | A bright hiss, like an untuned radio | Covering sudden sounds, focus |
| Pink noise | Falls with frequency: 1/f | minus 3 dB per octave | Softer and rounder, like a waterfall | Sleep, a gentler all-night sound |
| Brown noise | Falls twice as fast: 1/f² | minus 6 dB per octave | A deep rumble, like rainfall or a shower | Relaxing, focus, people who dislike hiss |
"Often chosen for" is how these sounds are commonly used, not what research has proven. The research is further down.
What white, pink and brown noise actually are
Engineers sort noise by its power spectral density: how much power the sound carries at each frequency. For the colors of noise, that power is proportional to 1 divided by the frequency raised to some power, written 1/f^β. The value of β gives the color:
- White noise, β = 0. The power is flat, the same at every frequency. The name comes from white light, which mixes all visible colors. A perfectly white noise across all frequencies can't physically exist, because it would need infinite energy, so real white noise is flat only across a limited range, such as what we can hear.
- Pink noise, β = 1. The power falls in proportion to 1/f. That works out to minus 3 decibels per octave, and it means every octave carries the same amount of power. It sounds softer and duller than white noise.
- Brown noise, β = 2. The power falls with 1/f², twice as steeply as pink: minus 6 decibels per octave. The name has nothing to do with the color. It comes from Brownian motion, the random jiggling of particles, and you can make brown noise by adding up (integrating) white noise over time. It's also called red noise.
Why white noise sounds so bright: "equal power per frequency" sounds balanced, but pitch works in octaves, and each octave doubles the frequency. The octave from 1,000 to 2,000 Hz is ten times wider than the octave from 100 to 200 Hz, so in white noise it carries ten times the power. Pink noise evens that out octave by octave, which is why many people find it more natural.
There are more colors. Blue and violet noise are the mirror image of pink and brown: their power rises with frequency, so they sound even brighter than white. Grey noise is shaped so it sounds even to the human ear. Green noise, which the Sleep Foundation describes as noise that boosts the middle frequencies, has limited research behind it for sleep, according to the same source.
How they sound
The easiest way to tell them apart is to listen to them one after another at the same volume:
- White noise is the hiss of an untuned radio or TV. It has a lot of energy in the high frequencies, which some people find sharp.
- Pink noise is often compared to a waterfall. The hiss is still there, but rounder.
- Brown noise loses almost all of the hiss. People describe it as rainfall or a shower; we describe ours in the app as distant surf or heavy rain.
If white noise feels harsh, try pink. If pink still feels too bright, try brown.
Which noise is best for sleep?
Nobody has shown that one color is best. What the research does show is more cautious than most "best noise for sleep" lists:
- The overall evidence is weak. A 2021 systematic review in Sleep Medicine Reviews looked at 38 studies of continuous white noise or similar broadband noise and sleep. Results ranged from noise improving sleep to noise disrupting it. Using the GRADE criteria, the authors rated the quality of evidence for continuous noise improving sleep as very low, and warned that it "may also negatively affect sleep and hearing."
- Falling asleep in a noisy moment. In a small 2017 study, 18 healthy adults went to bed 90 minutes earlier than usual to simulate a hard night. With broadband sound from two speakers at about 46 dB, the time to reach stage 2 sleep fell by a median 38% compared with the normal room noise. Small, one lab, and young healthy people, so it can't tell you what happens in your bedroom every night.
- Pink noise all night can change sleep. In a 2026 study in the journal Sleep, 25 healthy adults slept seven nights in a sleep lab with different sound conditions. Pink noise at 40 or 50 dBA reduced REM sleep compared with a quiet night. It slightly reduced the disruption caused by aircraft noise, but earplugs prevented nearly all effects of the environmental noise on sleep, though they started failing at the loudest level (65 dBA). The authors caution against "the widespread and indiscriminate use of broadband noise."
- A small pilot found the opposite for traffic noise. In a 2026 cross-over study of 12 healthy adults, continuous pink noise at 45 dB played through the night reduced the sleep disruption and blood markers linked to road, rail and air traffic noise. The authors ask for their results to be interpreted cautiously because the group was small and very similar. Together, the two studies suggest noise may help mask a noisy night but is not free of effects on a quiet one.
What this means in practice: noise is most useful when there's something to cover, like traffic, a snoring partner or a noisy building. In a room that's already quiet, it may add nothing, or even take something away. The NHS lists both options for a comfortable bedroom: "earplugs if noise is a problem" and "background sounds like rainfall, gentle music or white noise."
"Pink noise for deep sleep": what the studies really tested
You may have read that pink noise deepens sleep or improves memory. Those findings come from a different setup. In a 2017 study of 13 adults aged 60 to 84, a computer read their brain waves during sleep and played short pulses of pink noise timed exactly to the slow waves of deep sleep. That increased slow-wave activity while the pulses played, though not across the whole night, and improved word recall the next morning.
A pink noise track playing all night doesn't do this. It isn't timed to your brain waves, and the 2026 lab study above found that continuous pink noise reduced REM sleep. So "pink noise for deep sleep" is true for lab stimulation equipment, not for a sound machine.
Is brown noise bad for you?
There's very little research on brown noise specifically, and we found no study of its effects or side effects on sleep. What can be said applies to broadband noise in general:
- Too loud harms hearing, whatever the color (see the volume section below).
- All night isn't automatically harmless. The 2026 lab study tested pink noise, not brown. Because both are broadband noise, the authors urge caution overall and call for more research on the best color and level.
- It's a matter of taste. Some people find a low rumble soothing, others find it oppressive. How it feels to you is the best guide.
White, pink or brown noise for focus and studying
For work or studying, the idea is the same as at night: a steady sound can cover distracting ones, like conversations or a noisy street.
- In a 2022 study of 39 graduate students in a private office, white noise at 45 dB went with better sustained attention, accuracy and speed, more creativity and lower stress than the normal office sound. White noise at 65 dB helped working memory but raised stress. The authors note that earlier research in adults without attention problems shows mixed results.
- For brown noise and focus, we found no controlled study in adults that we could verify, even though it's a popular choice. It may simply be that many people find a low rumble less intrusive than a hiss.
Our takeaway: if you use noise to focus, keep it quiet, and notice whether it actually helps you or just fills the silence.
Masking: why steady noise hides sudden sounds
The idea behind all of this is masking. A sudden sound, like a door or a car, stands out against silence. The theory, as the Sleep Foundation puts it, is that a steady background masks such sounds and might make you less sensitive to unpredictable noise. Researchers still don't know for sure whether that is how noise helps some people sleep. The catch, as the 2026 study showed, is that the masking sound itself still reaches your brain all night.
How loud is safe?
There's no official guideline for the volume of noise at night, so the rule is simple: as quiet as still does the job. Two health authorities give hearing figures:
- The US National Institute on Deafness and Other Communication Disorders (NIDCD) says sounds at or below 70 dBA, even after long exposure, are unlikely to cause hearing loss, while long or repeated exposure to sounds at or above 85 dBA can cause it.
- The WHO says you can safely listen to 80 dB for up to 40 hours a week, but only 4 hours a week at 90 dB. It suggests keeping your device's volume below 60% of maximum, and gives a quick test: if you have to raise your voice to be heard by someone at arm's length, it's too loud.
For comparison, the WHO puts a library at about 40 dB and normal conversation at about 60 dB. The sleep studies above used about 40 to 50 dB, so a sleep sound can sit well below the level of a normal conversation.
Tips for tonight:
- Use a speaker, not earbuds, and place the phone away from your head, not on the pillow.
- Start quiet and go up only until the disturbing sound fades, not until the noise feels "full".
- Set a timer that fades out after you've fallen asleep, instead of playing noise all night.
- Try earplugs if the noise you want to block is loud. In the 2026 study they worked better than pink noise.
White, pink and brown noise in the app
AI Meditation: Sleep & Calm has these soundscapes, generated live on your phone rather than played from a looped recording, so there's no audible loop point:
- White noise, Pink noise and Brown noise, the three from this page.
- Blue noise, Violet noise and Grey noise, the brighter and ear-balanced colors.
- Deep tone, Warmth, Crystal and Resonance, soft tonal sounds; Resonance is a singing bowl tone.
- Free practice: silence with a singing bowl at the start and the end, for meditating on your own.
You can set a timer from 5 to 90 minutes, and the sound fades out and stops when the timer ends, or let it play until you stop it. If you'd rather fall asleep to a voice, there are guided sleep meditations and sleep stories, read by AI voices, and you can adjust how long a session lasts within its range. See how the app works, try it for free, no account needed.
Your health
This app is a wellness app and does not replace medical advice. If sleep problems last for weeks or affect your day, talk to a doctor. The NHS insomnia page explains when to see a GP and what treatment can look like.
Sources
All pages accessed on September 25, 2026.
- Woolf P. et al.: Noise Modeling: White, Pink, and Brown Noise, Pops and Crackles, in Chemical Process Dynamics and Controls, Engineering LibreTexts (CC BY 3.0). Power spectral density 1/f^β, white, pink, brown, blue and violet noise.
- Sound On Sound: Pink Noise (glossary). 1/f, equal power per octave.
- Sleep Foundation: White Noise: What It Is and How It Can Help You Sleep (updated July 29, 2025). Minus 3 dB per octave for pink noise, twice that for brown, how they sound, green noise, no official volume guideline.
- Riedy SM, Smith MG, Rocha S, Basner M: Noise as a sleep aid: A systematic review. Sleep Medicine Reviews 2021;55:101385.
- Messineo L. et al.: Broadband Sound Administration Improves Sleep Onset Latency in Healthy Subjects in a Model of Transient Insomnia. Frontiers in Neurology 2017;8:718.
- Basner M. et al.: Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep. Sleep 2026;49(5):zsag001.
- Vincens N. et al.: Pink noise reduces impact of traffic noise on sleep and the blood metabolome: a cross-over pilot study. Communications Medicine 2026;6(1):114.
- Papalambros NA. et al.: Acoustic Enhancement of Sleep Slow Oscillations and Concomitant Memory Improvement in Older Adults. Frontiers in Human Neuroscience 2017;11:109.
- Awada M. et al.: Cognitive performance, creativity and stress levels of neurotypical young adults under different white noise levels. Scientific Reports 2022;12:14566.
- NHS Every Mind Matters: How to fall asleep faster and sleep better. Earplugs and background sounds.
- NIDCD: Noise-Induced Hearing Loss (last updated April 16, 2025). 70 and 85 dBA.
- WHO: Deafness and hearing loss: Safe listening (questions and answers, March 6, 2026). Safe listening times, 60% volume, decibel examples.
