Brown noise is a steady, deep, rumbling sound. If white noise is the hiss of an untuned radio, brown noise is a river heard from the next field, or the cabin hum of a long-haul flight. It contains the same random mix of frequencies as white noise, but with the energy concentrated at the low end, which is why it sounds rounder and less sharp.
People use brown noise for sleep for one main reason: it covers up the sounds that would otherwise wake them, without the fizzing quality that puts a lot of people off white noise. That covering-up effect, called masking, is well understood. Claims that brown noise does anything more than that, such as deepening sleep or calming the nervous system directly, are not backed by strong evidence, although many people do find it soothing.
What brown noise actually is
Every "colour" of noise is random sound spread across the range of frequencies we can hear. The colours differ in how that energy is shared out.
- White noise has equal energy at every frequency. Because our ears are most sensitive to high frequencies, it sounds bright and hissy.
- Pink noise has equal energy per octave, so it falls away by about 3 decibels with each octave you go up. It sounds like steady rain or a distant waterfall.
- Brown noise falls away faster still, by about 6 decibels per octave. The high frequencies are almost gone, leaving a low, soft rumble.
The name has nothing to do with the colour. Brown noise is named after Brownian motion, the random movement of tiny particles suspended in a fluid, first described by the botanist Robert Brown in 1827. A brown noise signal is generated by the same random-walk mathematics, which is why you will sometimes see it called red noise instead, by analogy with red being the low-frequency end of visible light.
The pink noise guide covers the middle option, and the rest of the Sleep Sounds guides cover rain, ocean and nature recordings.
Why brown noise sounds less harsh
Human hearing is most sensitive somewhere between roughly 2,000 and 5,000 hertz, which is the range of speech consonants and, unfortunately, the range where white noise sounds most piercing. Brown noise has very little energy there. What remains is the kind of low-frequency sound we tend to find non-threatening: wind, surf, a boiler, traffic on a distant motorway.
That matters at bedtime. Sound that is even slightly grating keeps a small part of your attention on it, which is the opposite of what you want. A sound you can genuinely ignore lets your attention drift, and drifting attention is what falling asleep feels like from the inside.
In short: Brown noise masks the same sounds as white noise, but with the high, hissy frequencies stripped away. That is why it feels softer, and why people who dislike white noise often get on with it.
What the evidence says
It is worth being honest here, because a lot of online enthusiasm outruns the research.
Masking is real. If a car door slams at 2am, what wakes you is the sudden jump from quiet to loud. A steady background sound raises the floor, so the jump is smaller and less likely to register. This is the reason steady noise helps light sleepers, people in flats with thin walls, and anyone sharing a bed with a snorer. If your problem is noise from outside, it is worth combining sound with the practical fixes in how to block out noise at night.
The rest is thin. A 2021 systematic review by Riedy and colleagues in Sleep Medicine Reviews looked at studies of continuous noise as a sleep aid and found the overall quality of evidence low, with results pointing in different directions. Most studies used white or pink noise rather than brown, most were small, and some suggested noise could slightly disturb sleep rather than help it. Nobody has shown in a good trial that brown noise in particular improves sleep quality, deepens sleep or reduces anxiety.
So the fair summary is: brown noise is a reliable way to mask disruptive sound, and a sound that many people find pleasant to fall asleep to. It is not a treatment for insomnia. If you are regularly lying awake for reasons that have nothing to do with noise, the difficulty falling asleep guide is a better starting point, and persistent problems are worth raising with a GP.
How to play brown noise at night
You have three realistic options.
A phone or tablet
Free brown noise tracks and apps are everywhere, and this is the easiest way to find out whether you like it. The drawbacks are notifications, adverts, a bright screen at the wrong moment and a battery that has to last the night. Use a long track rather than a ten-minute video, turn on do-not-disturb, and put the phone face down.
A sound machine
A dedicated machine sits on the bedside table, has a physical volume dial and often a timer, and does not buzz with messages. Fan-based machines make genuine white noise with a real fan and cannot produce brown noise. To get brown noise you need a digital machine that generates it, and the better ones do so continuously rather than looping a recording. The white noise machine buying guide explains what to look for.
Sleep headphones
If you share a bed with someone who wants silence, or you want the sound close without filling the room, headband-style sleep headphones keep flat speakers against your ears without anything pushing into the ear canal when you lie on your side. Small sleep earbuds are the other option, and some add a little passive noise blocking of their own.
If you want brown noise without a phone by the bed
A digital machine generates brown and pink noise as well as white; headband headphones keep the sound personal in a shared bed.
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Digital sound machine with multiple noise colours
Example: LectroFan (Classic or Evo)
LectroFan machines are marketed as producing a range of fan sounds and white-noise variations digitally, with the manufacturer stating the sounds are generated rather than recorded loops. They include a timer and volume control.
- Best for
- Choice of white, pink and brown-style sounds and fan sounds
- Key feature
- Non-looping digitally generated noise with many variants and a timer
- Why it may help
- If you want to experiment with brown or pink noise rather than only white, a multi-sound digital machine lets you find the tone that suits you best.
- Worth knowing
- Some people prefer the softer character of a fan-based machine; check the UK power adapter.
Headband sleep headphones
Example: SleepPhones; CozyPhones; Musicozy
Headband headphones put flat speakers inside a stretchy fabric band that doubles as a light-blocking eye cover for some people. Models are marketed as wired or Bluetooth, with the speakers usually removable so the band can be washed.
- Best for
- Side sleepers who want audio without anything inside the ear
- Key feature
- Thin, flat speakers inside a soft fabric headband
- Why it may help
- Ordinary earbuds press into the ear when you lie on your side. A headband keeps the speaker flat against the ear so you can listen to sleep sounds or guided relaxation comfortably.
- Worth knowing
- Audio quality is basic and bass-light; the band can feel warm in summer; battery life varies by model.
Getting the volume right
Brown noise is easy to turn up, because it does not sound loud in the way a hiss does. Resist that.
- Set it at the level of a quiet conversation in the next room, or lower. You should be able to talk over it easily.
- If you are using it to mask a specific noise, aim to soften that noise rather than drown it out. You will not achieve silence, and chasing it means ever-higher volume.
- Keep it at a level where you would still hear a smoke alarm, a child, or someone at the door.
- Do not put a speaker right by your head at any real volume, and be especially careful with earbuds, where the sound has nowhere to go but your eardrum.
Prolonged exposure to loud sound damages hearing, and eight hours a night adds up. Anything that leaves your ears feeling dull or ringing in the morning is far too loud. The NHS hearing loss pages are a sensible reference if you are unsure.
For babies the advice is more cautious: keep any device well away from the cot, at a low volume, and follow NHS guidance on safe infant sleep.
Is it a crutch?
A common worry is becoming unable to sleep without it. What people usually mean is that they have learned to associate the sound with settling, much as they associate their own pillow with sleep. That is a habit, not a dependence, and it is harmless as long as a phone or portable machine can travel with you.
If it still bothers you, use a timer so the sound fades out after an hour. Most people are asleep well before then. There is a fuller discussion in is it bad to sleep with white noise on all night, and everything there applies equally to brown noise.
Where to go next
Tonight, play a brown noise track at a volume you barely notice and see whether the flat feels quieter. If it does, that is your answer. If it feels oppressive, try a rain recording, which has a similar softness with a little more texture.
And if the noise you are trying to cover is not the real reason you are awake, sound can only do so much. The Quiet the Mind guides are the place to go when it is thoughts, not traffic, keeping you up.
Frequently asked questions
Is brown noise better than white noise for sleep?
Neither has been shown to be better in good-quality trials. Both mask disruptive sounds. Brown noise concentrates its energy in lower frequencies, so it sounds softer, and many people prefer it for that reason. If white noise sounds harsh to you, brown noise is the obvious thing to try next.
Can I listen to brown noise all night?
At a low volume, well below normal speech, most adults can. Keep it quiet enough that you could still hear a smoke alarm or a child calling. If you would rather not run it all night, a timer that fades it out after an hour or so covers the time it takes most people to fall asleep.
Why is it called brown noise?
It is named after Brownian motion, the random jiggling of tiny particles first described by the botanist Robert Brown in 1827. The signal that produces brown noise follows the same mathematics as that motion. The name has nothing to do with the colour brown, which is why you also see it called red noise.
Sources and further reading
- NHS: Insomnia
- NHS Every Mind Matters: How to fall asleep faster and sleep better
- Sleep Medicine Reviews: Noise as a sleep aid: A systematic review (Riedy et al., 2021, Sleep Medicine Reviews)
- NHS: Hearing loss
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Written and reviewed by the Quiet Mind Sleep editorial team in line with our editorial policy. Spotted an error? Let us know.