Noise colors compared
| Color | Sounds like | How the energy is spread | Best for |
|---|---|---|---|
| White | Static, a fan, TV hiss | Equal at every pitch | Covering sudden sounds, focus |
| Pink | A steady shower, rain | Falls 3 dB per octave | Falling asleep, a soft all-rounder |
| Brown | A waterfall, strong wind | Falls 6 dB per octave | Masking traffic and snoring |
| Green | Wind in trees, distant surf | Gathered around 500 Hz | Relaxing, a more natural feel |
White noise
White noise has the same energy at every pitch, so it sounds bright and hissy. That evenness is what makes it good at covering sudden sounds like a door, a dog or voices in the hall.
It's also the best-studied noise for babies. In a randomized study of 40 newborns (Spencer et al., Archives of Disease in Childhood, 1990), 80% fell asleep within five minutes with white noise, compared with 25% without it.
Keep it quiet, though. When researchers tested 14 infant sleep machines at full volume (Hugh et al., Pediatrics, 2014), all of them were louder than the 50 dBA limit recommended for hospital nurseries when measured 30 cm away. Use a low volume, keep the speaker away from the crib, and set Auto-stop.
Pink noise
Pink noise turns the high pitches down, so each octave carries the same energy. It sounds fuller and softer than white noise, which is why many people find it easier to sleep to.
Pink noise is also the sound used in deep-sleep research. In the lab, short bursts of pink noise timed to sleepers' brain waves strengthened deep sleep and improved overnight memory (Ngo et al., Neuron, 2013). In 13 adults aged 60 to 84, memory gains were three times larger than on a night without the sound (Papalambros et al., Frontiers in Human Neuroscience, 2017). Those studies used precisely timed pulses, not steady noise, but they're why pink noise has a reputation as the sleep color.
Brown noise
Brown noise turns the highs down even further, so it's mostly deep rumble. It's named after the botanist Robert Brown and the random “Brownian motion” he studied, not after the color.
Brown noise went viral with people who have ADHD, who say it quiets a busy mind. There isn't much research on brown noise itself yet. The closest study (Söderlund et al., Journal of Child Psychology and Psychiatry, 2007) found that background white noise helped children with ADHD on a memory task, while slightly hurting the performance of other children.
Green noise
Green noise is a popular, informal name for noise gathered in the middle of the range, around 500 Hz, without the hiss of white noise or the rumble of brown. There's no single official definition, so recordings vary. Many people say it sounds the most like nature.
SleepHz's Green Noise is centered on 500 Hz. If it sounds too soft, try pink noise; if you want more depth, try brown.
Which noise color is best for sleep?
- Brown noise if low sounds keep you up, like traffic, an air conditioner or a snoring partner.
- Pink noise if you want the softest all-rounder, or you're curious about the deep-sleep research.
- White noise if sudden sounds wake you, like doors, footsteps or voices.
- Green noise if the others sound artificial and you'd like something closer to nature.
- Prefer real nature sounds? Try Rain & Thunder or Ocean Waves.