White, Pink, Brown and Green Noise: A Complete Guide

Noise “colors” sound like a marketing idea, but the first three are precise descriptions of how a sound’s energy is spread across pitch. The fourth, green, is looser. This guide keeps two things apart: what each color is, which is a matter of measurement, and what people link with listening to it, which is a matter of evidence.

What a noise color means

A noise color describes a sound’s spectrum: how much power it has at each frequency. The names borrow from an analogy with light, where white light mixes all colors. Some of the names have standard definitions in certain fields, while others are informal and loosely defined.

One idea helps with everything below. We hear pitch in octaves, and each octave covers twice as many hertz as the one beneath it. The span from 500 Hz to 1,000 Hz is 500 Hz wide, and the span from 1,000 Hz to 2,000 Hz is 1,000 Hz wide. So “equal power at every frequency” and “equal power in every octave” are different recipes.

Color	Power per hertz	As pitch rises by an octave	What it sounds like
White	Equal at every frequency	Stays flat	A bright hiss
Pink	Proportional to 1/f	Falls 3 dB	A softer, fuller wash
Brown (red)	Proportional to 1/f²	Falls 6 dB	A deep, low roar
Green	Not standardized	Varies	Extra energy in the middle pitches, in most uses

White noise

White noise has a flat spectrum: the same power at every frequency. Played as sound, it is heard as a hiss, a bit like a long, steady “h” breathed out. Because the highs take up so many hertz, a lot of the energy sits in the upper pitches, which is why it can sound sharp.

Strictly, perfect white noise is a theoretical model. Real sounds are white only across the range that matters, and over the range we can hear, that is good enough.

Pink noise

Pink noise has equal energy in every octave, which means its power per hertz falls by about 3 dB with each octave (3.01 dB, to be exact). It is also called 1/f noise. Compared with white noise, the highs are turned down and the low and middle pitches come forward, so it sounds less hissy. One reference compares it to a waterfall.

Pink noise has a practical job outside listening: engineers play it through speaker systems and measure the result to check that the sound is even across the spectrum.

Brown noise

Brown noise falls faster: 6 dB per octave (6.02 dB), with power proportional to 1/f². Most of the energy sits in the low pitches, and the highs are strongly reduced. It sounds like a low, soft roar, a bit like a waterfall, heavy rain or distant thunder.

The “brown” is not a color at all. It honors Robert Brown, who described Brownian motion, the random jiggle that produces this kind of spectrum. It is also called red noise, which comes back to the light analogy.

Green noise: a name without a fixed meaning

Here honesty matters, because green noise is not a standardized term the way white, pink and brown are. Reference sources list several different uses:

the middle part of white noise, used in halftone dithering for images
bounded Brownian noise
noise shaped like the human voice, used for testing audio equipment
a sound similar to pink noise with more energy near 500 Hz, described by one author as the background sound of the natural world

A mathematician’s blog that looked into the idea found the same thing: the colors beyond the standard few are not rigorously defined, and one rainbow-style way of dividing the hearing range would put green around the middle, where hearing is most sensitive. That blog was clear that this was one reading, not a standard.

For listeners, this means a “green noise” track from one source may not sound like one from another. Read the name as a loose label for a noise with extra middle pitches, and trust your ears over the name.

The other colors, briefly

Blue noise rises by 3 dB per octave over a limited range, and violet noise rises by 6 dB per octave, the mirror image of pink and brown. Gray noise is white noise adjusted by an equal-loudness curve, so that it is meant to seem equally loud at every pitch.

What research says about listening

The color definitions above are facts about spectra. Whether listening to one of them does anything is a separate question, and the answers are weaker.

Bedtime noise. A systematic review of 38 studies on continuous noise and sleep (Riedy and colleagues, 2021) found that studies disagreed: some reported that continuous noise helped, others that it disrupted. The authors rated the quality of the evidence as very low, noted that the studies varied widely in noise, measurements and design, and advised against promoting it until better studies exist. They also noted that noise could affect hearing. Evidence label: Emerging / Mixed.

Concentration and memory. A large review of noise and performance (Szalma and Hancock, 2011) pooled 242 studies and found that results depend on whether the noise is continuous or intermittent, the type of noise and the task. In one laboratory study of healthy adults (Rausch and colleagues, 2014), white noise slightly raised recognition memory for pictures, and a plain tone did not. Evidence label: Emerging / Mixed.

Claims about one color being best. We could not find verified research that compares pink, brown and green noise and shows that one is better for anything. Those claims are common online, but we label them Traditional / Unproven.

These labels rate the evidence for what people link with the sounds, not the sounds themselves. Liking a sound, or seeing it played widely, does not raise a label.

Trying them comfortably

Noise is steady and easy to forget about, so check your volume now and then. Keep it low, no louder than a quiet conversation, and stop if anything feels uncomfortable. Try each color for a few minutes on its own before you layer anything.

Brown noise, rain and other steady sounds are the kind of thing you can try and layer at a low volume in OscillaMind, which is coming to Android first. OscillaMind is for listening and routines, not medical care. If you have a health concern, talk to a doctor.

FAQ

What is the difference between white and brown noise? White noise has equal power at every frequency, so it sounds like a bright hiss. Brown noise loses 6 dB with each octave upward, so it sounds like a deep, soft roar.

Is green noise a real standard? Not in the way white, pink and brown are. The name is used for several different things, so it can sound different from one source to the next.

Which color should I choose? There is no verified research that one is best. Choose by what you find comfortable, and keep the volume low.

What does research say about noise at bedtime? The best review we found rated the evidence as very low in quality, with mixed results, so we label it Emerging / Mixed. If you try it, keep the volume low.

Sources

Colors of noise (reference entry). https://en.wikipedia.org/wiki/Colors_of_noise
White noise (reference entry). https://en.wikipedia.org/wiki/White_noise
Pink noise (reference entry). https://en.wikipedia.org/wiki/Pink_noise
Brownian noise (reference entry). https://en.wikipedia.org/wiki/Brownian_noise
John D. Cook, Green noise and Barks. https://www.johndcook.com/blog/2016/04/27/green-noise-and-barks/
Riedy, Smith, Rocha & Basner (2021), Noise as a sleep aid: A systematic review, Sleep Medicine Reviews. https://www.em-consulte.com/article/1421191/article/noise-as-a-sleep-aid-a-systematic-review
Szalma & Hancock (2011), Noise Effects on Human Performance: A Meta-Analytic Synthesis, Psychological Bulletin. https://peterhancock.ucf.edu/noise-and-human-performance-a-meta-analytic-synthesis/
Rausch, Bauch & Bunzeck (2014), a laboratory study of white noise and recognition memory, Journal of Cognitive Neuroscience. https://pubmed.ncbi.nlm.nih.gov/24345178/