How many colors of noise are there?
Six are in routine use: white, pink, brown (also called red or brownian), blue, violet (also called purple) and grey. Five of them are defined purely by the slope of their spectrum; grey is the odd one out, defined by human hearing rather than by mathematics.
Other names circulate — black, green, orange, and so on — but they have no agreed technical definition and are used inconsistently, so they are best treated as marketing rather than engineering. Everything below is generated by the Harmonoise noise generator, so you can hear each difference as you read about it.
Noise colors chart: the six colors compared by spectral slope, sound and typical use.
| Color | Slope (dB/octave) | Sounds like | Common use |
|---|---|---|---|
| White | Flat, 0 dB/oct | Radio hiss, static | Masking, broadband testing |
| Pink | −3 dB/oct | Steady rain | Room and speaker calibration |
| Brown | −6 dB/oct | Waterfall, distant thunder | Sleep, deep masking |
| Blue | +3 dB/oct | Thin, airy hiss | Dithering, high-frequency tests |
| Violet | +6 dB/oct | Sharp, sibilant | High-frequency tinnitus therapy |
| Grey | Equal-loudness weighted | Even across the range | Hearing tests, psychoacoustics |
What "color" means for noise
In audio, "noise" is a random signal, and its "color" describes how that randomness is distributed across frequencies. A noise signal is pure in a statistical sense, not in a pitched sense: there is no musical fundamental, no chord, no melody. What differs between colors is the shape of the spectrum — how much energy sits in low versus high frequencies on average.
The names come from a loose analogy to light. White light is an even mix of visible wavelengths, and white noise is an even mix of audio frequencies. Pink noise has more "warmth" at the bottom of the spectrum, like light skewed toward the red end. The analogy is imperfect — there is no literal wavelength mapping — but the vocabulary stuck.
White noise
White noise has approximately equal energy per hertz across the audible range. On a flat display it looks like a thick horizontal band; on an A-weighted meter it still sounds bright because the ear is more sensitive to mid and high frequencies. Use cases include: speaker and room testing where a broadband reference is needed, masking unwanted sounds when concentration matters, and creating a neutral background in home studios. White noise is the simplest to generate — each sample is an independent random value — and is the common ancestor of all the other colors.
Pink noise
Pink noise has equal energy per octave, which means energy falls by about 3 dB per octave as frequency rises. Because the ear groups frequencies roughly into octaves, pink noise tends to sound balanced and natural — less harsh than white noise but not especially muffled. It is the industry default for room tuning and loudspeaker calibration. When a live-sound engineer plays a reference signal through a PA and walks the room with a measurement microphone, pink noise is typically the signal they use. It is also a popular choice for sleep and focus audio because it is easier on the ears than white noise over long listening sessions.
Brown noise (also called brownian or red noise)
Brown noise falls roughly 6 dB per octave, giving it a deep, rumbling character reminiscent of a distant waterfall or heavy rain behind glass. The name is not a reference to color at all — it comes from Brownian motion, the random walk of particles in a fluid. A running integral of white noise produces a brown-noise-like signal, which is why many implementations describe it as a smoothed or integrated random walk. People who find white or pink noise too bright often prefer brown noise for relaxation, tinnitus relief, or ambient backgrounds. To hear it, try it in the brown noise generator.
Blue noise
Blue noise is the mirror image of pink: it rises about 3 dB per octave, emphasizing high frequencies. It sounds hissy and airy rather than deep. Its most widely cited application is in digital signal processing — specifically, dithering. When an audio signal is converted from higher to lower bit depth, adding a small amount of blue noise as dither distributes the quantization error away from the low- and mid-frequency ranges where the ear is most sensitive, so the noise that remains is less perceptible.
Violet (purple) noise
Violet noise rises about 6 dB per octave, making it the high-frequency counterpart to brown noise. Its energy is concentrated at the very top of the spectrum, producing a thin, sharp hiss. Violet noise is used in specialized applications such as certain kinds of tinnitus therapy, as a test signal for high-frequency transducers, and as a building block in more complex audio processes. It is also the derivative of white noise in the discrete-time sense, which is why many software generators implement it by differentiating white samples.
Grey noise
Grey noise is designed to sound uniform across the spectrum to a human listener rather than flat on a measurement meter. It applies an equal-loudness contour so that frequencies the ear is more sensitive to are attenuated, and frequencies it is less sensitive to are boosted. The result is a noise that feels evenly weighted at any point in the audible range. Grey noise is common in psychoacoustic experiments and hearing tests where perceptual uniformity matters more than mathematical flatness.
Picking a noise for a task
- Room and speaker calibration: start with pink noise. It approximates the average long-term spectrum of music and is what most calibration guides assume.
- Focus and concentration: pink or brown noise usually feel less fatiguing than white over long periods. Personal preference varies, so experiment.
- Sleep: brown noise is a common pick for heavier masking and a "warm" feel.
- Infant sleep masking: any steady low-volume noise can help, but keep volume conservative — long exposure at loud levels is not recommended.
- Audio testing: white noise is the simplest reference for verifying a broadband signal path; pink noise is better for frequency-balance work.
- Dithering and DSP experiments: blue or violet noise are the usual high-frequency tools.
- Hearing tests and perceptual experiments: grey noise is the most perceptually uniform baseline.
How volume affects everything
Most "which noise should I use" questions are actually loudness questions in disguise. Any noise becomes harsh at high volume and pleasant at low volume. Calibrate with your ears: start quieter than you think you need, then raise the level until the noise just masks what you want to mask. For long listening sessions, a level you can comfortably hold a conversation over is usually a reasonable ceiling.
Frequently asked questions
What does colored noise mean?
A noise color describes how a steady random signal's energy is spread across frequencies: white is flat, pink and brown tilt toward the bass, blue and violet tilt toward the treble. A single event such as a thump or a knock has no noise color, although deep, rumbling sounds are often compared to brown noise.
What other colors of noise are there besides white, pink and brown?
The other established colors are blue (+3 dB per octave), violet (+6 dB per octave) and grey (shaped to sound equally loud at every frequency). Names such as black, green and orange also circulate, but they have no agreed technical definition.
Which noise color blocks out sound best: white, pink or brown?
Match the noise to the sound you want to cover. Brown noise masks low rumble such as traffic or a neighbor's bass, pink noise covers voices and general household sound, and white noise is most effective against high-pitched hiss or whine. Pink is the usual all-round compromise.
Is grey noise the same as brown noise?
No. Brown noise has a fixed slope of −6 dB per octave and sounds deep and rumbling. Grey noise follows an equal-loudness curve, boosting the lowest and highest frequencies the ear hears poorly, so it sounds evenly balanced rather than dark.
What color of noise sounds like people talking in the background?
None of the standard colors. A blur of overlapping voices is called babble noise, and a steady noise shaped like the average spectrum of speech is called speech-shaped noise. Its spectrum is closest to pink noise, but the rhythm of voices makes babble sound different from any steady colored noise.
How do colors of noise help with music?
Pink noise is the standard signal for calibrating studio monitors and PA systems, and some engineers use it as a reference when balancing a mix. Blue-weighted noise is used when dithering to a lower bit depth, and white noise is a common raw ingredient in sound design for risers, sweeps and snare layers.
Try it
You can generate each of these noises directly in your browser using the Harmonoise Noise Generator, and export them as WAV files at common sample rates and bit depths for use in a DAW, a sleep playlist, or a measurement chain. If you already know which one you want, go straight to the white noise generator, the pink noise generator, the brown noise generator, or the grey noise generator.