White, pink and brown noise: what is the difference?
"White noise" gets used for any steady hiss, but white, pink and brown noise are three different sounds. All three are random noise. What changes is how the sound's energy is spread between low and high pitches, and that changes how harsh or deep it sounds.
White noise: bright and hissy
White noise has the same energy at every frequency. There are far more high frequencies than low ones, so that even spread comes across as bright and hissy, like an untuned radio. It is the best of the three at covering sharp, high sounds such as voices, but many people find it tiring over a whole night.
Pink noise: softer and more even
Pink noise has less energy as the pitch goes up: each octave carries the same total energy, instead of each octave carrying double the one below it. To the ear this sounds more balanced, closer to steady rain or wind in leaves, and noticeably less harsh than white noise. It is a good middle ground if white noise feels too sharp.
Brown noise: deep and rumbling
Brown noise (also called red or Brownian noise, after the random "Brownian motion" it is modelled on, not the colour) drops off even faster as the pitch rises. Most of its energy is in the low end, so it sounds like a deep roar: distant surf, a far-off waterfall, or the inside of a plane. Many people find it the most relaxing of the three, and it is the best at covering low sounds like traffic rumble.
Side by side
| Noise | Sounds like | Good at covering |
|---|---|---|
| White | Radio static, hiss | Voices, high sounds |
| Pink | Steady rain, wind | A bit of everything |
| Brown | Deep roar, distant surf | Traffic, rumble, bass |
Which one should you use?
There is no single best colour. It mostly comes down to what you find comfortable and what you are trying to cover. A simple way to choose:
- Start with pink. If it feels too thin, try brown. If voices still get through, try white.
- To cover a noise, match the sound to it: high noise needs a bright sound, low noise needs a deep one. See covering up noise.
- Keep the volume low. It only needs to be loud enough to blur the sounds you don't want.
Natural sounds work the same way. Rain sounds a lot like pink noise, and a waterfall or heavy surf a lot like brown. If plain noise feels too clinical, rain, a waterfall or a fan do a similar job.
Does one colour help you sleep or think better?
You will see strong claims online, especially for pink and brown noise. There is much less research behind them than those claims suggest. The sleep guide and the focus guide go through what has actually been studied.