Blue Noise

What Blue Noise Actually Sounds Like

Blue noise is thin, airy and very bright. Everyday comparisons are a steam valve letting off steam, an aerosol can held down, the spray of a shower without the drumming on the floor, or the long ring of a cymbal after it is hit. It is only the very top of the sound, with the body taken away.

If white noise sounds sharp, blue noise is sharper still. It has almost no weight: nothing underneath and nothing to fill the room. On headphones it seems to float just above and outside your head. That unusual feeling is part of why some people enjoy listening to it for a minute or two.

A minute or two is about the honest recommendation. Most people do not want this sound on for eight hours. The rest of this page explains why, and what blue noise is really for.

Why It Sounds So Bright

Blue noise is pink noise turned upside down. Pink noise gets quieter as the pitch goes up. Blue noise gets louder, by the same amount.

We measured the blue noise on this player, and it follows the ideal blue noise pattern closely. We make it the same way as our pink noise, but in reverse, so the two are exact mirror images.

The result is that blue noise puts almost all of its sound in the high range where our hearing is sharpest. Play blue noise and brown noise at the same power, and they do not sound equally loud at all. The blue one is painful and the brown one is barely there. That is why we set all five colours on this site to the same loudness as your ear hears it, not to the same power. Without that, switching to blue would be a nasty surprise every time.

Where Blue Noise Really Matters: Pictures, Not Sound

Blue noise is a real and important technical term, but it belongs mainly to printing, images and computer graphics, not to sleep sounds. This explains why the phrase appears so often in technical writing and almost never in sleep research.

The classic reference is Robert Ulichney's Dithering with blue noise (Proceedings of the IEEE, 1988; 76(1):56–79). It made blue-noise dot patterns the standard way to print pictures with tiny dots. The idea is clever. When you turn a photo into black and white dots, you must add small errors. You want those errors to be as fine-grained as possible, because the eye is worst at seeing very fine detail. Hide the errors where the eye cannot follow them, and the picture looks clean.

The same idea appears all over computer graphics, because fine-grained errors are the hardest kind to see. In sound recording, engineers use the same trick when they prepare digital audio: they push unavoidable noise to where the ear notices it least.

In every one of these cases, the point of blue noise is that you will not notice it. That is very different from playing it into your ears at a volume where you certainly will.

What Blue Noise Is Actually Good For as a Listening Sound

There are only a few real uses, so here they are without padding.

Covering high-pitched noises. A steady sound covers best when it is at the same pitch as the noise you want to hide. Some sounds that bother people are high: a whine from a laptop, a squealing fan, a high electronic whistle, or the click of a keyboard across the desk. The deeper colours will not touch these, but blue noise will. This is the one job where blue beats the other four.

Short sessions for one task. Fifteen minutes of blue noise while you deal with one specific noisy machine is a sensible use. It is not a bedtime sound.

Training your own ears. Listen to blue noise right after brown noise. It is the fastest way to understand how the colours differ, and it makes the other four much easier to tell apart afterwards.

Blue noise is in the app as well as in this web player. If it turns out to suit your problem, you can use it offline and on a timer like the others.

What Blue Noise Is Bad At

Sleeping. Everything that makes blue noise useful in printing makes it a poor sound for the night. It is bright and tiring, it has no deep sound to settle into, and no research of any kind supports it for sleep. If a page recommends blue noise for sleep, it is probably just listing every colour, not telling you anything useful.

Low noise of any kind. Traffic, air conditioning or a heating system, footsteps overhead, a neighbour's bass: blue noise does nothing about any of them. Turning it up makes your room louder without making theirs quieter. Use brown noise instead.

Hours of listening. Blue noise puts its sound where the ear is most sensitive. That same high range is the one most linked to hearing damage from noise. So it is the colour where volume matters most. The risk from any sound depends on how loud it is and how long you hear it, not on its colour. But at the same loudness, blue noise puts the most sound into that sensitive range. Keep it quiet, keep it short, and do not fall asleep to it on headphones.

Tinnitus, in most cases. Tinnitus, a ringing or hissing in the ears, is often high-pitched. A bright sound can sit right on top of it. Some people find that helps, and others find it makes things much worse. People react very differently, and this site cannot predict how you will react. Most people who use noise to cover tinnitus end up with a deeper colour. There is more on the brown noise for tinnitus page. None of this is medical advice. If you have tinnitus, talk to an audiologist (a hearing specialist).

How It Compares With the Other Colours

Line up the colours from deep to bright, and blue is at the bright end: brown is the deepest, then pink, then white, then blue. Green noise does not belong on that line at all, because it boosts the middle sounds instead of leaning one way.

For almost every reason people visit a noise site, such as sleeping, focusing, or covering a road or a conversation, one of the other four is the better choice. Blue noise earns its place here for three reasons. It is a real sound with a real definition. It is the right tool for one specific, uncommon problem. And leaving it out would mean pretending the colours stop at white.

Frequently Asked Questions

Related pages

• Brown Noise for Sleep — The free web player, plus the full guide to brown noise for sleep, focus, and tinnitus.
• Noise Colour Test — Two questions and a listening test to find your noise colour.
• White Noise — The flat, bright colour, and the best of the five at making speech impossible to follow.
• Brown Noise Generator — A real brown noise generator in your browser: made live as you listen, with no file and no loop.
• Pink Noise — The balanced, natural-sounding colour: a good default, and the sound engineers use to test speakers.
• Green Noise — The middle colour: pink noise with the middle sounds made stronger, and the only one of the five with no standard definition.
• Brown Noise — The deepest colour: a steady rumble that is best for traffic noise and long nights.
• Blue vs White Noise — Brighter than white noise: the one high-pitched job blue does better, and why white noise already covers most of it.
• Brown Noise for Tinnitus — Masking versus getting used to tinnitus, why the pitch of your tinnitus decides the colour, and where sound therapy really sits in the 2014 medical guideline.
• Brown Noise App — Which brown noise app to install, whether it is really free, and what an app can do that a browser tab cannot.