Blue noise
The mirror of pink: energy rises with pitch, giving a bright, airy hiss.
Layers — mix as many as you like
Tap a second sound to layer it — rain under brown noise, for instance.
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What is blue noise?
Blue noise is pink noise turned upside down. Instead of losing 3 decibels per octave it gains 3, so energy increases as pitch rises and the sound becomes distinctly bright. It is rarely used for sleeping — most people find it too sharp for that — but it has serious uses elsewhere: it is the noise of choice for dithering in digital audio and for distributing points evenly in computer graphics, because its energy sits above the range where artefacts are noticeable.
This page is a blue noise generator: the sound is computed in your browser rather than streamed from a file, so it starts instantly and never reaches a loop point. More on how that works.
Good for
- Curiosity and comparison rather than sleeping
- Masking high-pitched sounds specifically
- Anyone working with audio dithering or graphics sampling
The details
- Spectrum
- Rises 3 dB per octave — the mirror of pink
- Also called
- Azure noise
- Sounds like
- A thin, bright hiss with little body
- Used in
- Audio dithering, image dithering, graphics sampling
Questions
Is blue noise good for sleep?
Generally not. Its energy is concentrated exactly where the ear is most sensitive, so it is fatiguing over long periods and offers no advantage over gentler colours for masking. If a bright sound suits you, white noise is the more comfortable version of the same idea.
What is blue noise actually used for?
Mostly outside sleep. In digital audio it is used for dithering, where a small amount of shaped noise removes the distortion that comes from reducing bit depth — putting that noise high in the spectrum keeps it out of the way. In computer graphics, blue-noise point distributions look more even and natural to the eye than purely random ones.
How is blue noise different from violet noise?
Both rise with frequency; violet rises twice as steeply, at 6 decibels per octave against blue's 3. Violet is the mirror of brown, blue is the mirror of pink. In practice violet sounds even thinner and more piercing.
Every colour of noise
White noise
Equal power at every frequency — the bright hiss that masks almost anything.
Play white noise →Brown noise
Deep and low, like a distant waterfall. The most popular colour for sleeping.
Play brown noise →Green noise
Mid-range noise, often described as the background sound of open countryside.
Play green noise →Pink noise
The middle ground: softer than white, brighter than brown. Close to steady rain.
Play pink noise →Grey noise
Shaped so every frequency sounds equally loud, rather than measuring equally loud.
Play grey noise →Violet noise
The mirror of brown: rises 6 dB per octave into a thin, piercing hiss.
Play violet noise →Black noise
Effectively silence, with almost all energy below what you can hear.
Play black noise →Beyond the colours
Not noise colours in the strict sense, but built from them — and useful for the same reason.
Rain
Steady rainfall with the patter on top — the most requested sleep sound there is.
Play rain →Fan
A box fan running in the corner, without the draught or the electricity bill.
Play fan →Ocean
Slow waves arriving and drawing back, roughly ten to a minute.
Play ocean →Thunderstorm
Rain with distant thunder rolling through at irregular intervals.
Play thunderstorm →