Free online blue noise generator

What is blue noise?

Blue noise is the mirror image of pink noise. Pink loses about 3 decibels with every octave you go up; blue gains 3 decibels instead, so its energy climbs steadily from the bass to the treble. Both are defined by that slope, which makes blue one of the formally specified colors, alongside white, pink, brown and violet, rather than a loose description like green.

The result is a fine, bright hiss with very little body underneath it. Where brown noise is a rumble and white is static, blue is closer to a spray of water or escaping steam. It is the only color here whose energy rises with frequency, which is exactly what separates it from white, which is flat, and from grey, which is dipped where the ear is keenest.

What blue noise can mask

The case for blue is specific, and it is worth being plain about it: most people should not start here. Blue puts its energy where human hearing is most sensitive, so at the same volume it fatigues faster than pink or brown, and it masks low rumble hardly at all.

It earns its place when the sound disturbing you is itself high-pitched. A color only masks what it overlaps, and a pipe hissing behind the wall, a keyboard in the next room, birds at 5am or the whine of a charger all sit up in the range where brown and green have nothing to offer. Blue covers them at a lower volume than white would need, because it spends none of its energy on the bass those sounds do not occupy.

It is also the color to try if white noise reads as dull or muddy to you rather than harsh. That is the less common complaint, but a real one, and blue is the only color that answers it. If white already feels sharp, go the other way, to pink or grey.

How loud should you set it?

Lower than any other color. Because blue sits in the band your ears are tuned for, a level that seems modest at bedtime can feel piercing at 3am once the room has gone quiet around it. Start well below where you would set white, and raise it only until the specific high-pitched sound you are covering stops registering.

Use the fade in, and judge it over a full night rather than a ten second sample: a bright hiss is at its most impressive in the first minute and at its most wearing in the eighth hour. The full three-step method is here.

How this generator actually works

Nothing here is recorded. The audio is generated in your browser by a port of the generator that runs inside the Veil app, with the app's production settings.

It starts from the same Paul Kellet cascade that produces pink noise. Pink falls 3 decibels per octave. Taking the difference between each sample and the one before it is a differentiator, which rises 6 decibels per octave, so differencing pink gives a clean 3 decibel per octave rise: blue, by definition, from the same cascade Veil's pink and green already use.

Two choices make this version less sharp than textbook blue. A little unshaped white noise is mixed underneath the tilt, at 30 percent, because blue on its own has almost no low end. A low-pass at 6 kHz also caps the top octave. Both are adjustable in the app.

Two independent cascades run in buffers of about 30 and 37 seconds, with coprime sample counts, and are mixed together, so the combined pattern takes well over a year to come back around, with each loop boundary crossfaded against real continuation samples rather than faded to silence.

Try the other colors.

Which color works is personal, and a minute of listening settles it faster than any chart. Each of these is a live generator like this one: White noise Pink noise Brown noise Green noise Grey noise. Or hear all six side by side. If noise is not the right texture, there are also seven fan sounds.

Blue noise for sleep, in depth