River and Green Noise for Focus
Running water with a steady hiss underneath, for a desk where the room keeps interrupting you.
- Green Noise 60%
- River 35%
Noise Colors Explained: White, Pink, Brown and More
Noise colors are names for the mix of pitches in a steady, hissy sound. White noise spreads its power evenly across frequency, so it arrives as a bright hiss. Pink noise drops by 3 dB per octave as the pitch rises, which makes it softer, closer to steady rain. Brown noise drops twice as fast, 6 dB per octave, so most of what reaches you is deep rumble. The colors tell you what a sound is like. They promise nothing about your sleep, your focus or your health.
Noise colors comparison
| Noise color | Power change as frequency rises | Typical character | Practical use |
|---|---|---|---|
| White | Even across frequency | Bright, even hiss, like static | Blurring voices and sharp sounds |
| Pink | −3 dB per octave | Softer hiss, like steady rain | A gentler background |
| Brown / red | −6 dB per octave | Deep rumble, like a waterfall | Covering traffic and boilers |
| Blue | +3 dB per octave | Crisp, bright hiss | Audio testing |
| Violet / purple | +6 dB per octave | Very sharp hiss | Audio testing and signal work |
| Grey | Shaped so each pitch sounds about as loud | Even to the ear, and it varies by recording | Hearing and audio checks |
| Green | No agreed definition | Usually mid-pitched or nature-like | A listening label; check the recording |
Those numbers describe the recording, not how loud it will feel to you. Your speakers or headphones, the level you choose and your own hearing all change what comes out.
Why noise has colors
The names borrow from light. White light holds all the visible colors at once, and white noise holds every frequency at once in the same measure. Engineers then reached for other color names as they described other shapes of sound.
Your ears do not hear pitch in even steps. An octave up from a low hum covers a narrow stretch of frequencies; an octave up from a high hiss covers a much wider one. White noise gives every stretch the same power, so the top octaves end up carrying most of the sound and it comes out bright. Pink noise turns the high pitches down until each octave carries about the same amount. Brown noise turns them down twice as far, so what you hear is mostly a deep rumble.
A color name says nothing about how a recording moves. Two pink-noise tracks can match on paper and still differ in how steady they hold, whether you can hear the loop, and how they wear on you after an hour.
White noise
White noise carries the same power in every equal slice of the frequency range, and you hear that as a bright, even hiss. Most people compare it with radio static, rushing air or a fan running hard.
It blurs voices and sharp sounds better than brown noise does: the edges of speech, keyboard clicks, a door down the hall. No sound erases a voice, because your brain keeps listening for speech, so what you get is words you can no longer make out.
At the same setting white noise sounds louder than brown, and the hiss tires some people, especially through headphones. Pink noise is the softer option if that happens to you.
Researchers have tested steady white noise for sleep and for attention, and the results are weak and mixed. Riedy and colleagues reviewed the sleep studies and rated the evidence very low quality. Nigg and colleagues pooled task studies in 2024 and found small gains for young people with ADHD or attention trouble, alongside small losses for those without. White noise is not a treatment for anything.
Play white noise in the browser.
Pink noise
Pink noise drops by 3 dB per octave as the pitch rises, which leaves each octave holding about the same power. That is why it sounds softer and more natural than white noise, nearer to steady rain or far-off surf.
It covers a wide range without leaning on the hiss, so it sits easier through a long evening. The trade is that it does less with sharp, high-pitched sounds than white noise at the same comfortable level.
Sleep laboratories have played short pink-noise pulses timed to the slow waves of deep sleep. That is a different thing from a track running all night, so nobody should sell you a pink-noise loop on the strength of those experiments.
Play pink noise in the browser.
Brown noise, also called red noise
Brown noise drops by 6 dB per octave, so it puts far more into the bass than white or pink noise and comes out as a deep rumble, like a waterfall heard from a distance. The name comes from Brownian motion, not from the color. Red noise is another name for the same sound.
That deep rumble is what covers traffic, a boiler, an air conditioner or the bass through a wall. It does little for voices. One catch: a phone speaker cannot really play deep sound, so brown noise through one will come out thin. Flat earbuds you can sleep on will do it, or a small speaker set on the floor or a shelf, well away from your pillow.
Direct research on brown noise and sleep or concentration is thin. What it is good for is masking a rumble you can point to. Read the science and limits of brown noise, or how white and brown noise sound to someone with tinnitus.
Play brown noise in the browser.
Blue noise
Blue noise climbs by about 3 dB per octave, the mirror image of pink noise. It holds more of the high pitches and sounds brighter than white noise.
Audio engineers use it for testing and for dithering, where the deep end of the sound would only get in the way.
The brightness turns uncomfortable quickly, so it makes a poor default for sleep, for long headphone sessions, or for anyone whose ears are sensitive to high sounds.
Play blue noise in the browser.
Violet noise
Violet noise climbs by about 6 dB per octave, the mirror image of brown noise. It pushes still more of the sound toward the top of the range.
It belongs to testing and signal work more than to listening. It can sound piercing, so keep the level down and stop if it hurts. If you read that violet noise treats tinnitus, that claim needs a clinician behind it; nothing about the sound itself shows that.
Grey noise
Grey noise is shaped so that every pitch in it sounds about as loud as every other to a typical listener. There is no one grey-noise recording, because how loud a pitch seems shifts with the level you play it at and with whose ears are listening.
Audio engineers and hearing researchers use it for listening tests.
A grey-noise track off the shelf cannot be matched to your hearing, your headphones and your level at once, so treat it as a rough fit.
Play grey noise in the browser.
What about green noise?
Green noise has no agreed definition, nothing like the settled meanings of white, pink and brown. Some generators use the label for a mid-pitched sound, others for filtered pink noise, others for something nature-like. The name alone will not tell you what you are about to hear.
So look up what the provider means by it, or just listen and judge the recording on its own. Two green-noise tracks can sound nothing like each other, and neither one comes with a health effect attached.
Play Slo’s green-noise version or combine it with water in the River and Green Noise preset.
Which noise color should you choose?
Start from the sound you want to soften, and from what your speakers or earbuds can actually play. Every color on this page has its own player here, so you can compare them by ear in the browser before you install anything.
| Situation | First choice | Reason to change |
|---|---|---|
| Voices and sharp room noise | White or pink | Switch if the hiss starts to tire you |
| Traffic or a low mechanical hum | Brown | Switch if the bass sounds uneven |
| General background for reading | Pink | Try silence if it pulls at your attention |
| Bright morning atmosphere | Blue, kept quiet | Skip it if high sounds bother you |
| Audio or hearing test | The color the protocol names | Do not swap by preference |
| A “green noise” recommendation | Listen to the actual recording | The label is not standardized |
For sleep, focus or study, the color is only one part of it. A sudden peak, an audible loop, the volume, where the speaker sits and what you happen to like can all matter more. Our direct brown, white, and pink noise comparison goes deeper on the three common options.
Listen safely
Play it at the lowest level that still covers what you are trying to cover. Background sound for sleep or work should never feel like it is pressing on you. The World Health Organization advises adults to keep average personal-audio exposure below 80 dB and to cut the listening time as the level rises.
Keep your alarm, the doorbell and the people near you audible. If your ears ring, if sound goes muffled, or if you feel worn down by it, turn the level down or turn it off.
Noise-color presets
Hear a noise color inside a soundscape
Compare green noise with flowing water or use a low brown-noise base for focused work. Adjust each layer rather than raising the whole mix.
Deep Work Studio
A steady rumble, a wide ambient sound, and typing quiet enough that you barely catch it.
- Brown Noise 48%
- Deep Focus 32%
- Keyboard Typing 9%
Frequently asked questions
How many noise colors are there?
There is no fixed count. White, pink, brown (also called red), blue, violet and grey have settled technical meanings. Other labels, green and black among them, change from one generator to the next.
What is the difference between white, pink, and brown noise?
White noise spreads its power evenly across frequency, so you hear a bright hiss. Pink noise drops by 3 dB per octave and sounds softer. Brown noise drops by 6 dB per octave and comes out as a deep rumble.
Which noise color is best for sleep?
No color has been proven best for everyone. Brown noise suits a deep rumble like traffic, pink noise makes a soft general background, and white noise blurs voices and sharper sounds better. Pick the one that covers what actually wakes you, at the lowest level that works.
Which noise color is best for focus?
Brown or pink noise is a fair place to start, because neither has words in it and both are easier on the ears than white noise. No research shows a focus benefit for everyone. Try the same task with the sound and in silence, then keep whichever left you less distracted.
Is green noise a real noise color?
It is a popular label with no agreed definition. Two generators can put out quite different sounds under that name. Judge the recording by ear, because the word alone will not tell you what you are getting.
Research referenced
- Riedy and colleagues (2021), Noise as a sleep aid: A systematic review.
- Nigg and colleagues (2024), Do White Noise or Pink Noise Help With Task Performance in Youth With ADHD or Elevated Attention Problems?.
- Ngo and colleagues (2013), Auditory Closed-Loop Stimulation of the Sleep Slow Oscillation Enhances Memory.
- World Health Organization (2026), Deafness and hearing loss: Safe listening.
Each color has a bedtime preset that opens ready to play: brown, pink, white and green.
Related guides
- Brown Noise vs White Noise vs Pink Noise
- Best Sounds for Focus
- Best Sounds for Deep Sleep
- How to Use Sound Mixing
Want more textures to compare? The Slo app carries a larger library and keeps the mixes you save.
Explore more sounds in Slo
Stack two or three sounds, keep the blend, and let the timer stop it. Slo, on iOS, Android and Mac.
