White, pink and brown noise are all random sound, spread across every frequency we can hear. What makes them different is the balance: white noise has equal energy at every frequency and sounds like a bright hiss; pink noise tilts toward the low end and sounds like steady rain; brown noise tilts further and sounds like a deep rumble or a waterfall. Which is best is mostly personal, but the research has a few useful things to say.
The three colours
| Noise | How the energy falls | Sounds like |
|---|---|---|
| White | It doesn't: flat across frequencies | A hiss: radio static, a fan, a hair dryer |
| Pink | Halves with every octave up (−3 dB) | Steady rain, wind in leaves, surf |
| Brown | Quarters with every octave up (−6 dB) | A waterfall, heavy surf, a jet cabin |
Brown noise is named after Brownian motion, the random jiggling of particles described by the botanist Robert Brown, not after the colour. White noise takes its name from white light, which mixes all visible colours, and pink noise from the reddish tint you'd see if light had the same tilt.
How noise helps at all
The main effect is masking. Concentration and sleep are broken less by loud sound than by sudden change: a voice, a door, a phone. A steady background raises the level those sounds have to reach before you notice them, so fewer get through. Every colour of noise does this; they differ in which sounds they cover best and in how pleasant they are to listen to for hours.
What the research says
- Focus: Göran Söderlund and colleagues found that background white noise improved memory performance in children with attention difficulties, while slightly hurting it in children without them. The idea that a little noise helps under-aroused brains is promising but still being tested, and results vary.
- Sleep: pink noise has the most interesting results. In a 2013 study, Hong-Viet Ngo and colleagues played short bursts of pink noise timed to sleepers' slow brain waves and found deeper slow-wave sleep and better memory the next day. That was precisely timed stimulation in a lab, though, not a noise machine left on all night.
- Overall: a 2021 systematic review of noise as a sleep aid found the quality of the evidence low. Noise clearly helps some people, especially in noisy places, but it's not a proven treatment.
- Brown noise became popular online around 2022, mainly on word of mouth. There's little research on it specifically; many people simply find it less harsh than white noise.
Which one to choose
- An open office or chatty café: white or pink noise covers speech best.
- Long writing or coding sessions: brown or pink. Easier to forget about for hours.
- Sleep: pink or brown, quiet, with a timer to fade it out.
- Low hums (traffic, an air conditioner, a fridge): brown noise, which is strongest in the same range.
Whichever you use, keep it quiet: just loud enough to mask what bothers you, and not at full volume through headphones for hours. Try all three on the white noise generator, or something recorded, like rain or an airliner cabin, which sounds a lot like brown noise with character.
How loud should it be?
Quieter than you think. The aim is to cover distractions, not drown out the world: about the level of a quiet conversation or softer is enough for most rooms. For sleep, set it just loud enough that small sounds stop waking you, and put the speaker across the room rather than by your head. Through headphones, keep the volume well below the maximum; long hours of loud sound can damage hearing. When researchers tested infant sleep machines, some could get loud enough to be a concern at full volume, so for babies keep machines low and away from the cot.
Headphones or speakers?
- Speakers work for sleep and for a room of your own, and are kinder to your ears over long periods.
- Headphones work in shared spaces. Noise-cancelling headphones remove steady background hum on their own, so you need less added noise on top.
- Both: keep sessions sensible, and take the headphones off on your breaks.
The sound of a flight
Flight, our focus timer, plays a real cabin recording while you work, with rain, waves and other sounds to choose from. Your session is a flight, and the hum stops when you land.