Last updated: October 2026
White noise is the most popular sleep aid that nobody prescribes. Millions of people fall asleep to a fan, an app or a bedside machine every night, and the colour-noise trend has added pink and brown to the menu. This guide covers what the research actually shows, which colour does what, when steady noise can make sleep worse, and the difference between masking sound and sound designed to work on sleep itself.
Quick answer: White noise helps some people sleep by masking sudden sounds that would otherwise wake them, and it works best in noisy environments: traffic, a snoring partner, thin walls. The evidence that it improves sleep in a quiet room is weak, and a 2021 systematic review found the research overall is poor quality with some signs of harm. Pink noise has the best evidence of the three colours for deeper sleep, but only in laboratory studies where it was timed to brain waves, which no app does. Brown noise has no sleep studies at all. Keep any noise quiet, below about 50 decibels, and keep machines well away from a baby's cot.
What is white noise, and what are pink and brown noise?
All three are broadband noise, meaning they contain every audible frequency at once. The colour describes how the energy is spread across those frequencies.
| Colour | How it is made | What it sounds like | Sleep evidence |
|---|---|---|---|
| White | Equal energy at every frequency | Untuned radio static, a hair dryer. Bright and hissy | Mixed. Helps in noisy settings; weak or negative in quiet ones |
| Pink | Energy falls as frequency rises, so bass and treble sound balanced to the ear | Steady rain, wind in trees, a waterfall at a distance | Best of the three, but from lab studies that timed it to slow waves |
| Brown | Energy falls faster still, so it is almost all low frequency | A river in flood, a jet from inside the cabin, low thunder | None. Popular for focus and tinnitus; no sleep trials |
Most people find white noise harsh and pink or brown more comfortable, which is why rain and ocean tracks dominate the sleep playlists. The ear is the right judge here: the colour that does not annoy you is the one you will leave on.
Does white noise help you sleep?
It depends almost entirely on how noisy your bedroom is.
Where it helps: in a loud or unpredictable environment. A 2016 study in the Journal of Caring Sciences played white noise to patients on a coronary care unit, one of the noisiest places anyone sleeps, and found their sleep quality held up where the control group's deteriorated; the mechanism is masking. A sudden sound (a door, a car, a snore) wakes you because of the jump from quiet to loud. Raise the background level and the jump shrinks, so the sound no longer registers. If you live on a main road, share a bed with a snorer, or sleep in a flat with thin walls, this is real and useful.
Where it does not: in a room that is already quiet. A 2021 systematic review in Sleep Medicine Reviews (Riedy and colleagues, University of Pennsylvania) went through 38 studies of continuous noise as a sleep aid and found the evidence low quality and inconsistent, with some studies showing worse sleep and more fragmentation. The authors' conclusion was that there is not enough evidence to recommend white noise for sleep in general, and a possibility it does harm by keeping the auditory system working all night.
So the honest answer is: white noise is a tool for a noisy room, not a sleep improver. If your bedroom is quiet and you sleep badly, the cause is something else, and our guides on falling asleep fast and staying asleep all night cover the usual ones.
Is pink noise better than white noise for sleep?
Pink noise has the only strong result in this field, and it comes with a catch.
In a 2017 study at Northwestern University (Papalambros and colleagues, Frontiers in Human Neuroscience), older adults slept in a lab wearing EEG sensors while short bursts of pink noise were played in time with their slow brain waves during deep sleep. The bursts increased slow-wave activity and improved next-morning memory recall. A 2013 study in Neuron (Ngo and colleagues) had found the same in younger adults. This is called closed-loop acoustic stimulation, and it is the basis for the claim that pink noise deepens sleep.
The catch is the word "in time". The effect came from sound delivered at a precise moment in the brain-wave cycle, detected by EEG. An app or machine playing steady pink noise all night is not doing that. Whether continuous pink noise deepens sleep is unproven; what it reliably does is sound less harsh than white noise, so it masks just as well with less irritation. That alone is a fair reason to choose it.
What about brown noise?
Brown noise became popular on social media as a focus aid, especially among people with ADHD, and many find its low rumble soothing. There are no published sleep studies on it. It masks low-frequency disturbance well (traffic, a neighbour's bass, a boiler) and most people can tolerate it louder than white noise without discomfort, which is both its appeal and its risk. If brown noise is what lets you sleep, use it; just keep the volume down.
Which colour noise is best for sleep?
For masking, whichever one you find least irritating, which for most people means pink or brown. For deepening sleep, none of them reliably, because the studies that showed it used timed bursts rather than a continuous track. If you want one rule: start with pink at the lowest volume that covers the problem sound, and stop using it if your sleep does not improve within two weeks, because then noise was not the issue.
Can white noise be bad for you?
Three concerns are worth taking seriously.
- Volume, especially for babies. A 2014 study in Pediatrics tested 14 infant sound machines and found several could exceed 85 decibels at the cot, the level at which workplaces require hearing protection. Keep any machine at least two metres from a cot, at the lowest effective volume, and not on all night. The same caution applies to adults using earbuds.
- Dependence. If you can only sleep with noise on, you will struggle in hotels, at friends' houses and on nights the power goes. It is a habit the brain learns, so it is worth occasionally sleeping without it.
- Keeping the ear busy. The 2021 review's concern: continuous sound keeps the auditory pathway active all night, which may fragment sleep in a quiet room even if you do not remember waking. Trackers cannot see this; an EEG can.
Rule of thumb from the research: keep bedroom sound below about 50 decibels, roughly the level of a quiet conversation in the next room, and use a timer so it stops once you are asleep if your room is otherwise quiet.
Masking sound versus sound that works on sleep
Every colour noise does the same job: it covers other sounds up. It does nothing to the sleep cycle itself. A different category of device uses sound as a signal rather than a blanket.
The Sleep Engine Pod is one. It plays patented neuroacoustic soundwaves, low-frequency sounds in a programmed sequence, from a module under or behind your pillow, at a volume at the edge of hearing. The sequence is designed to guide the brain through the natural order of its sleep cycles over the night, with Fall Asleep, Deep Sleep, Easy Sleep and Power Nap programmes. It is not a noise machine: it is barely audible, it does not mask anything, and it is quiet enough that a partner is not disturbed.
Sleep Engine Pod
Barely audible neuroacoustic sound from under your pillow, designed to guide sleep cycles rather than mask noise. Nothing to wear, free app, no subscription. Tested in two independently run clinical studies.
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The evidence, stated as carefully as the white noise evidence above: in a 21-night study run by CMR, an independent research company, 36 adults with insomnia symptoms went from 4.2 to 6.8 hours of sleep a night and woke 55 percent less often. In a second study, improvements on the PSQI sleep quality scale after 12 weeks were still present eight weeks after stopping. Across both, 94 percent reported sleeping better. These are small studies and group averages; individual results vary, and most of the gain arrived in week two. If you have a noisy bedroom, it does not replace masking; if you have a quiet one and still sleep badly, it is addressing a different problem from the one white noise addresses.
Three things that beat any noise
If the aim is deeper sleep rather than a quieter room, sound is low on the list. A cool bedroom around 18C, no alcohol in the evening and a consistent wake time move deep sleep more than any track. And if the thing waking you is your own bed, no sound will fix it: a mattress that holds heat, transfers a partner's movement or has started to dip produces exactly the brief wakings that noise is supposed to prevent. Every mattress in our hybrid mattress collection uses open-cell foam and independent pocket springs for those three reasons, and our guide to the best mattress for couples covers motion isolation specifically.
Frequently asked questions
Is it OK to play white noise all night?
In a noisy room, yes, at a low volume. In a quiet room there is no benefit and a possible cost, because continuous sound keeps the auditory system active; use a timer so it switches off once you are asleep. Keep it below about 50 decibels and well away from a baby's cot.
What colour noise is best for sleep?
Pink, for most people: it masks as well as white noise and sounds less harsh. The lab evidence that pink noise deepens sleep came from bursts timed to brain waves, not continuous playback, so treat "deepens sleep" claims from apps with caution. Brown noise has no sleep studies.
Is brown noise better than white noise?
For comfort and for masking low-frequency sound such as traffic, usually yes. For sleep quality, there is no evidence either way on brown noise, and only mixed evidence on white. Choose by what you can tolerate at low volume.
What are the downsides of white noise?
Volume (several baby machines exceed safe levels at the cot), dependence (you cannot sleep without it), and possible fragmentation in a quiet room from keeping the ear working all night. A 2021 review found the overall research low quality with some signs of harm.
Is white noise safe for babies?
Only at low volume and at a distance. A 2014 Pediatrics study found some infant sound machines could exceed 85 decibels at the cot. Keep it at least two metres away, as quiet as works, and not running all night. If in doubt, ask your health visitor.
Does white noise help with a snoring partner?
It can, because snoring is exactly the kind of irregular sound masking works on. Pink or brown noise usually covers it with less harshness than white. If the snoring is loud with pauses, the snorer should see a GP about sleep apnoea rather than the partner buying a louder machine.
Sources: Riedy SM et al., Noise as a sleep aid: a systematic review, Sleep Medicine Reviews, 2021; Papalambros NA et al., Acoustic enhancement of sleep slow oscillations and concomitant memory improvement in older adults, Frontiers in Human Neuroscience, 2017; Ngo HV et al., Auditory closed-loop stimulation of the sleep slow oscillation enhances memory, Neuron, 2013; Hugh SC et al., Infant sleep machines and hazardous sound pressure levels, Pediatrics, 2014; Farokhnezhad Afshar P et al., Effect of white noise on sleep in patients admitted to a coronary care unit, Journal of Caring Sciences, 2016; Messineo L et al., Broadband sound administration improves sleep onset latency in healthy subjects in a model of transient insomnia, Frontiers in Neurology, 2017; Sleep Engine clinical study summaries as published on the product page, October 2026.
