Brown, white or pink noise for sleep

The names sound like marketing, but they describe something real: how a sound’s energy is spread from low pitches to high ones. Pick the right one and the dripping tap, the traffic or the television through the wall slips into the background. Pick the wrong one and you’re lying awake listening to a hiss.

What the colours mean

White noise has the same energy at every frequency. Because there are far more high frequencies than low ones, and our ears are most sensitive in the upper-middle range, it sounds bright: the hiss of an untuned radio, or the rush of air from a fan.

Pink noise gets quieter as the pitch rises, by about 3 decibels every octave, so each octave carries the same energy. It sounds softer and more even than white noise. Steady rain, or a waterfall heard from a distance, is close to pink.

Brown noise falls away faster still, about 6 decibels per octave, which leaves a deep rumble: heavy surf, a strong wind, the inside of a plane. It’s named after the botanist Robert Brown and the random “Brownian” motion the signal resembles, not after the colour. You’ll also see it called red noise.

You may come across other colours in apps, such as green noise. They aren’t standard terms. Usually they mean noise shaped to boost the middle of the range, and the label varies from app to app.

How noise helps, and what it can’t do

A steady noise doesn’t make your room quieter. It raises the background level, so that changes stand out less: a car door, a cough, a floorboard. What wakes most of us is the change, not the loudness itself, and a sound that starts against near-silence is a much bigger change than the same sound against a steady hush.

Masking works best when the noise covers the same pitches as the thing you want to hide.

• High-pitched sounds, like voices, birds, a hissing radiator or a ticking clock, are covered well by white or pink noise.
• Low rumbles, like traffic, bass through a wall or the low notes of a partner’s snoring, need energy down low. That is brown noise’s job.

It’s worth being honest about the research. In 2021 a systematic review of 38 studies rated the evidence that continuous noise improves sleep as very low quality. Some studies found people fell asleep faster, others found no difference, and at least one found more disturbed sleep. The studies were small and varied a lot in how loud the noise was and how sleep was measured. So treat noise as something to try, not a cure. Plenty of people find it helps; that’s worth knowing, but it isn’t proof.

Choosing one for your room

Start from what keeps you up:

• City traffic, a neighbour’s music, snoring: start with brown noise.
• Voices, a TV through the wall, a ticking clock: try pink, then white if pink isn’t enough.
• Nothing in particular, you just like a steady background: pink is usually the easiest to live with for a whole night.

If the noise itself starts to bother you after ten minutes, change colour before you give up on the idea. A sound you don’t notice is doing its job; a sound you keep noticing isn’t.

Natural sounds are noise too. Steady rain behaves much like pink noise, and surf or a waterfall leans brown. If plain noise feels clinical, rain may do the same job more pleasantly. You can also layer them: a quiet brown noise under rain fills in the low end that rain lacks.

Keep it quiet

• Use the lowest volume that still does the job, and set it at bedtime rather than during the day, when the room is louder and you’ll set it too high.
• Put the speaker across the room rather than next to your head.
• For a baby’s room, take extra care. A 2014 study measured 14 infant sleep machines and found that at full volume every one was louder, at 30 cm, than the 50 dB limit recommended for hospital nurseries, and some were far louder. The authors suggest keeping a machine well away from the cot, at a low volume, and not running it all night.
• A timer that fades out means the noise stops once you’re asleep, if you don’t need it all night.

Trying it in Uyu

Uyu has white, pink and brown noise made for the app, alongside its recordings of rain, water, wind and rooms. A good first night: Brown Noise at around 40%, Rain on top, and a 60-minute timer with the fade turned on. If you wake up hearing it, it’s too loud.

Sources

• Riedy SM, Smith MG, Rocha S, Basner M. Noise as a sleep aid: a systematic review. Sleep Medicine Reviews. 2021;55:101385.
• Hugh SC, Wolter NE, Propst EJ, Gordon KA, Cushing SL, Papsin BC. Infant sleep machines and hazardous sound pressure levels. Pediatrics. 2014;133(4):677–681.