White, pink and brown noise
What do the colours describe?
White noise has equal power per hertz. Because we hear frequencies in octaves, higher octaves contain more hertz, so white noise sounds bright, like "shhh".
In pink noise the power falls in inverse proportion to frequency; every octave carries equal energy, and it sounds more balanced, like a waterfall. In brown (Brownian) noise the power falls faster still; the sound is deep, rumbling and muffled.
Blue and violet noise are the opposite: power rises with frequency (3 dB per octave for blue, 6 dB for violet), and the sound is thin and hissy. Grey noise is shaped by the ear's sensitivity: it is filtered with the inverse of an equal-loudness contour (ISO 226), so to an average ear it sounds roughly equally loud at every frequency. The contour is an average; because hearing varies from person to person, grey noise does not sound equally balanced to everyone. In our noise generator the bass boost of grey noise is limited so it does not strain speakers.
Masking
A continuous sound raises the threshold at which other sounds in similar frequency bands can be heard; this is an established psychoacoustic phenomenon. That is why noise is used to cover speech, traffic or air-conditioning sounds. The level needed for masking adds its own hearing load: don't turn it up more than necessary.
Sleep
In some studies sleep-quality scores improved with white noise, but much of the evidence comes from special settings and its overall quality is low. In one laboratory study, adding pink noise to intermittent noise disrupted sleep structure further, while earplugs did better. If you use noise for sleep, keep it quiet and keep the source away from your bed.
Pink noise is often said to strengthen deep sleep. Those findings come from short sound pulses timed to brain waves with EEG during sleep, and even there the effect is small. Continuous pink noise played all night is a different method; in a 72-person study it did not increase insight. Continuous noise has not been shown to lengthen deep sleep.
Green, black and other names
"Green noise" is not a standard colour; it is an everyday name for noise with the middle frequencies (roughly 250-1000 Hz) brought forward. "Black noise" is mostly used to mean silence or near-silence. Definitions of these names vary between sources; in Frekans Studio, green noise is pink noise shaped with a band filter.
Does brown noise help focus?
In a meta-analysis of 13 studies, white and pink noise gave a small benefit on laboratory attention tasks in children and young people with high attention-problem symptoms, and slightly worsened performance in those without them. Brown noise was never tested. So the effect of noise on focus varies from person to person; a general "boosts focus" claim is not supported.
What does the evidence say?
Helps mask surrounding sounds.
◆ B · Moderate evidence- What do we know?
- Auditory masking is an established psychoacoustic phenomenon: a steady sound raises the detection threshold of other sounds in similar frequency bands. This is why noise is used to cover ambient sounds.
- What don't we know?
- It is not clear that masking translates into protected sleep: in a 25-person lab study, adding pink noise to intermittent environmental noise worsened sleep structure further, and earplugs worked better. A systematic review warns that continuous noise may also affect hearing.
Evidence on sleep is low quality and mixed; in one study pink noise reduced REM sleep. Keep the volume low.
▲ C · Preliminary/mixed evidence- What do we know?
- A meta-analysis of 12 randomized trials of white noise found better sleep-quality scores in adults and older adults; much of the evidence comes from intensive-care patients and infants. In a review of 34 studies, 19 reported positive results (only 6 of 18 for white noise). A 2025 systematic review of 7 randomised trials in hospitalised adults found white noise improved sleep efficiency and was well tolerated; the studies were small and varied, so no meta-analysis was possible.
- What don't we know?
- A systematic review of 38 studies rated the evidence 'very low' quality and warned that continuous noise may harm sleep and hearing. In a 25-person lab study, pink noise (50 dBA) reduced REM sleep by 18.6 minutes in one night. Some infant sleep machines were measured reaching hazardous levels at maximum volume.
The effect of noise on attention varies from person to person: small benefits in some, small harms in others.
▲ C · Preliminary/mixed evidence- What do we know?
- In a meta-analysis of 13 studies, white and pink noise gave a small benefit (g = 0.249) in children and young adults with ADHD or high attention-problem symptoms.
- What don't we know?
- In people without marked attention difficulties noise slightly worsened performance (g = −0.212), so it cannot be said to improve focus for users in general. Brown noise was never tested. Effects were measured on lab tasks, and appropriate levels are unknown.
Pink noise can be used to mask surrounding sounds during sleep; it has not been shown to lengthen deep sleep.
■ D · Insufficient evidence- What do we know?
- A meta-analysis of studies using short acoustic stimuli timed to brain waves in deep sleep (closed loop, with EEG) found a small, trend-level effect on memory consolidation (g = 0.25, p = 0.07).
- What don't we know?
- This app does not use EEG; continuous (open-loop) pink noise is a different method. In a 72-person study, overnight pink noise did not increase insight and shortened the first light-sleep period after sleep onset. The authors say the evidence is insufficient to recommend commercial devices.
Evidence levels and sources come from the database; the article adds no new claims. Evidence methodology
Frequently asked questions
- Which colour for focus?
- There is no reliable comparison showing which colour is "best"; it is mostly personal preference, and noise can slightly reduce attention in some people. Brown and pink noise sound softer and may be less tiring over long periods.
- Are noise machines safe for babies?
- Measurements found that some infant sleep machines reach hazardous levels at maximum volume. Frekans Studio offers no content for babies; don't play loud sound through speakers near them.
Listen and try
Last updated: 3 October 2026 · This article is for information only; it is not medical advice.