White, pink or brown noise: which one helps you sleep?
They aren't marketing names. Each one is a different shape of sound, and the right one is mostly the one you can stand all night.
Sound machines and apps love offering a palette of noise colours. It sounds like branding, but the names describe something real: how the energy in a sound is spread between low and high pitches.
What the colours mean
White noise has equal energy at every frequency. Because our ears are more sensitive to higher pitches, it sounds bright and hissy, like an untuned radio or a television between channels.
Pink noise turns the high end down as it goes up. Each step up in pitch carries a little less energy than the one below it. To most ears it sounds more balanced and softer than white noise. Steady rain on a roof is close to pink.
Brown noise (sometimes called red noise) turns the high end down even further. It's mostly rumble: a waterfall heard from a distance, wind, the low roar inside an aeroplane.
There are other colours, but these three are the ones you'll find on almost every machine.
What the research says
Less than the packaging suggests. Some small studies have found that steady noise helps people fall asleep faster in noisy places, and there is interesting early work on pink noise and deep sleep. But the studies are small, the results are mixed, and nobody has shown that one colour is right for everyone.
What is well established is the masking effect. A steady sound makes sudden sounds less jarring, because the jump from background to bark or hoot is smaller. Any of the three colours does that.
How to choose
Try each one for a few nights rather than a few minutes. Something that sounds pleasant for thirty seconds can grate after an hour.
- If the noise that bothers you is high-pitched (voices, hooting, a neighbour's television), white or pink noise covers that range better.
- If it's low-pitched (traffic rumble, music bass, a generator), brown noise has more energy down there, though low sounds are hard to mask completely.
- If you just want something to listen to, pink is the usual starting point because most people find it the least tiring.
Keep it gentle
The point is to soften the edges of other sounds, not to drown them. A few guidelines:
- Set the volume to the lowest level that does the job. You should be able to hold a quiet conversation over it.
- Put the speaker across the room, not on the pillow.
- For babies, keep machines well away from the cot and quiet. Paediatric guidance warns against loud machines close to infants.
- Phones work, but a cheap dedicated machine or a fan means your phone isn't lighting up beside the bed at 03:00.
And if you find you can't sleep without it, that's fine. Plenty of people have slept beside a fan their whole lives.