NoiseCurbWhite noise has equal energy at all frequencies; pink and brown noise have more energy in the low end, so they sound softer and deeper. A 2021 systematic review rated the evidence that continuous noise improves sleep as very low. Pink noise benefits came from short timed pulses, not all-night playback, and no studies of brown noise for ADHD were found. For babies, keep machines quiet and far from the crib.
White, pink and brown noise are everywhere now: sleep apps, sound machines and viral videos promising deeper sleep, better focus and calmer babies. The research is much thinner than the marketing. This guide explains what each color actually is, then grades the popular claims against the best available evidence.
What the colors mean
The "color" describes how a sound's energy is spread across pitches.
| Color | What it sounds like | How the energy is spread |
|---|---|---|
| White | A hiss, like a detuned radio | Equal energy at every frequency, so it sounds bright |
| Pink | Steady rain or wind | Energy falls as pitch rises, so it sounds softer and deeper |
| Brown (also called red) | A low rumble, like a waterfall or strong wind | Energy falls even faster, so the low end dominates |
None of these is a medical treatment. They are background sounds that change what you hear around you.
The evidence scorecard
| Claim | Verdict | What the research shows |
|---|---|---|
| Continuous noise helps you fall and stay asleep | Weak evidence | A 2021 systematic review of 38 studies rated the quality of evidence very low |
| Pink noise deepens sleep and boosts memory | Promising but narrow | Positive results used short pulses timed to brain waves, not a sound playing all night |
| Brown noise helps ADHD | Not established | A 2024 meta-analysis found no studies of brown noise at all |
| White or pink noise helps focus | Depends who you are | Small lab benefit for people with ADHD symptoms; slightly worse performance for others |
| Sound machines are safe for babies at any volume | False | Many infant machines can get far too loud, especially close to the crib |
| Noise masks distracting sounds | Yes, in principle | A steady background makes sudden sounds stand out less |
Sleep: what the best review found
The most thorough look at this question is a 2021 systematic review in Sleep Medicine Reviews (Riedy and colleagues), which assessed 38 studies. The authors concluded that the quality of evidence for continuous noise improving sleep was very low, which contradicts its widespread use, and noted that noise may also negatively affect sleep and hearing.
That does not mean it never helps. If sudden noises such as traffic or a snoring partner wake you, a steady background can reduce the contrast. It means the research does not yet show a reliable benefit for most people. Our guide to the quiet bedroom puts masking in context with other fixes.
Pink noise and deep sleep: read the fine print
Headlines about pink noise and memory usually trace back to a small 2017 study at Northwestern University. Thirteen healthy older adults heard very short pulses of pink noise, about 50 milliseconds each, timed by an algorithm to match the slow waves of their deep sleep. Their slow-wave activity increased and they remembered more words the next morning.
That is a genuinely interesting result, but it is not the same as leaving pink noise on all night. Another study published in 2023 found that overnight pink noise could actually interfere with some kinds of sleep-dependent learning. The honest summary: timed pulses are a research tool; continuous pink noise is not proven to deepen sleep.
Focus and ADHD: a mixed picture
A 2024 meta-analysis in the Journal of the American Academy of Child and Adolescent Psychiatry (Nigg and colleagues) pooled 13 studies. White and pink noise gave a small benefit on lab attention tasks for young people with ADHD or high ADHD symptoms, but a small negative effect for those without ADHD. The researchers found no studies of brown noise at all, despite its popularity online.
So if you have ADHD symptoms, background noise may help a little on some tasks. If you do not, it may slightly hurt. It is not a substitute for an ADHD evaluation or treatment. For the wider research on sound and concentration, see noise and focus.
Babies: volume and distance matter most
In a 2014 study published in Pediatrics, researchers tested 14 infant sleep machines at maximum volume. Every one exceeded 50 dBA, the recommended limit for hospital nurseries, when measured 30 cm (about 1 foot) away, and three exceeded 85 dBA.
Practical steps:
- Place the machine well away from the crib, never on the crib rail or inside it.
- Keep the volume low, and use the lowest setting that works.
- Consider a timer rather than all-night play.
Our guide to white noise for babies covers this in more detail.
Using noise safely if you like it
- Keep it moderate. About the level of a quiet conversation is a sensible ceiling for all-night use.
- Put distance between you and the source. Sound level drops as you move away.
- Choose the color you find least annoying. Many people find pink or brown noise less harsh than white.
- Check the level once. A free phone meter app gives a rough reading.
Myths worth dropping
- "Pink noise is proven to deepen sleep." Only timed pulses showed that, in a small study.
- "Brown noise treats ADHD." No studies of brown noise were found in the 2024 meta-analysis.
- "Louder masking works better." Louder simply means more sound exposure.
The short version
White, pink and brown noise can mask sudden sounds, but the evidence that they improve sleep or focus is weak. Pink noise research used timed pulses, not all-night playback. Brown noise for ADHD has not been studied. For babies, keep machines quiet and far from the crib. If a sound helps you, use it at a moderate level and see earplugs for sleeping for another option.
Questions people ask
Is brown noise good for ADHD?
It has not been studied. A 2024 meta-analysis found no brown noise studies. White and pink noise gave a small lab benefit for people with ADHD symptoms and slightly worse results for others.
Is it safe to sleep with white noise every night?
Keep it at a moderate level and away from your head. The evidence that it improves sleep is weak, and very loud noise all night adds to your sound exposure.
Does pink noise improve deep sleep?
A small study found that short pulses of pink noise timed to deep-sleep brain waves increased slow-wave activity. Continuous pink noise has not been shown to do the same.
How loud should a baby sound machine be?
Low, and far from the crib. In a 2014 Pediatrics study, all 14 machines tested exceeded 50 dBA at about 1 foot at full volume.
Sources
- Noise as a sleep aid: a systematic review (Riedy et al., 2021) · Sleep Medicine Reviewschecked
- Acoustic enhancement of sleep slow oscillations (Papalambros et al., 2017) · Frontiers in Human Neurosciencechecked
- Overnight exposure to pink noise could jeopardize sleep-dependent insight · PubMed Centralchecked
- Do white or pink noise help task performance in youth with ADHD? (Nigg et al., 2024) · JAACAPchecked
- Infant sleep machines and hazardous sound pressure levels (2014) · Pediatricschecked
This guide is general information, not medical advice. For sudden hearing loss, pain, discharge, dizziness or ringing in one ear only, see a doctor promptly. Medical disclaimer.