The best sleep sound is a steady one you find easy to ignore. White noise is bright and hissy, pink noise is softer and balanced, and brown noise is deep and rumbly, like heavy rain or wind. Research suggests sound mainly helps by masking disruptive noise, and the evidence that it improves sleep overall is still limited.
What the colours of noise mean
| Sound | What it is | Sounds like |
|---|---|---|
| White noise | Equal energy at every frequency | A detuned radio or a fan: bright and hissy |
| Pink noise | Energy falls by about 3 dB per octave, so each octave is equally loud | Steady rain or a waterfall: balanced and softer |
| Brown noise | Energy falls by about 6 dB per octave | Heavy rain, strong wind or distant surf: deep and rumbly |
| Nature sounds | Mixtures of the above with natural variation | Rain, ocean waves, a stream, forest |
What the research says
A 2021 systematic review of 38 studies rated the evidence that continuous noise improves sleep as very low quality (Riedy et al., 2021, Sleep Medicine Reviews). That does not mean it never helps; it means the studies are small and mixed. Where sound clearly helps is in masking: a steady sound makes sudden noises like traffic, doors or snoring less likely to wake you.
The exciting pink noise headlines come from a different technique. In lab studies, short bursts of pink noise timed to the brain's slow waves during deep sleep strengthened those waves and improved next-day memory (Ngo et al., 2013, Neuron; Papalambros et al., 2017). That needs equipment that reads your brain waves in real time, so it is not the same as playing pink noise all night.
Nature sounds vs noise
Rain, surf and wind are natural versions of pink and brown noise, with gentle variation that many people find more pleasant than a flat hiss. Others prefer pure noise precisely because it has no changes to notice. Try one for a week before switching.
How to use sleep sounds safely
- Keep it quiet: just loud enough to soften background noise.
- Put the speaker away from your head, across the room rather than on the pillow.
- Use a timer if sound wakes you later in the night.
- For babies, keep machines on low and well away from the cot. Some infant sleep machines exceeded safe levels at full volume when placed close (Hugh et al., 2014, Pediatrics).
Try them free
The Canopy & Tide mixer has rain, thunderstorm, ocean, wind, river, light rain and singing bowl sounds in 3D, with a sleep timer. For a full hour without a browser, see the videos on our YouTube channel.