Brown noise
The deepest of the three noise colours. Energy falls by 6 dB per octave, so almost everything you hear is below 500 Hz — a distant rumble with the hiss taken out. It is the one people who dislike white noise usually end up on.
Where the name comes from, and it is not the colour
Brown noise is named after Robert Brown, the botanist who described the jittering of pollen grains in water in 1827. Brownian motion is a random walk, and brown noise is what you get by integrating white noise — each sample is the previous one plus a small random step. The name is a pun on the other colour names rather than a description of a sound, and "red noise" is the same thing under a name that at least fits the pattern.
A pure random walk has a problem, and it is the one interesting engineering detail in this whole page: it never comes back. Left alone it wanders steadily away from zero, and that wandering is not audible — it is a slow drift towards direct current that no speaker can reproduce and that quietly eats all the headroom the rest of the mix needs. The generator here divides by a factor slightly above one on every step, which turns the walk into a leaky integrator: the same sound, but provably bounded and with a long-run average of exactly zero. The test suite runs two hundred thousand samples through it and checks both.
Brown noise, focus, and what actually got popular
Brown noise had a genuine moment on social media as an attention aid, particularly among people with ADHD, and the enthusiasm is not in doubt. The evidence is. There is a small body of work on white noise and attention in children with ADHD, some of it positive, most of it small and short; brown noise specifically has been studied very little, and the strong claims circulating online are extrapolations from anecdote rather than from findings. It would be dishonest to tell you otherwise, and this site is not going to.
What can be said without stretching: a lot of people find low-frequency noise less irritating than high-frequency noise over long periods, which matters if the sound is going to run for four hours. It masks the low rumble of traffic, plant machinery and neighbours better than white noise does, because that is where its energy is. And if you find it pleasant, that is a good enough reason to use it — enjoying a sound requires no scientific justification.
The reverse also happens and is worth naming. Some people find sustained low-frequency sound oppressive or slightly nauseating, in the same family as being near a running generator. If brown noise makes you feel that way after ten minutes, that is a real response, and pink noise or rain is the sensible next stop.
The three noise colours, side by side
The slope is the whole difference between them: how fast the power falls as frequency rises. Everything else — how bright it sounds, what it masks well — follows from that one number.
| Colour | Slope | What it is |
|---|---|---|
| White noise | 0 dB/oct | Equal power at every frequency. The reference the other two are shaped from, and the harshest of the three because human hearing is most sensitive where it has the most energy. |
| Pink noise | -3 dB/oct | Equal power per octave, which is how most natural broadband sound is distributed — rain, a waterfall, wind in trees. Reads as softer than white at the same loudness. |
| Brown noise | -6 dB/oct | The integral of white noise — a random walk. Almost all the energy is below 500 Hz, which is why it is the colour people reach for to cover traffic and voices through a wall. |
All three sliders are in the mixer above, so you can compare them directly rather than from a description.
Common questions
Is brown noise better than white noise for sleep?
Neither is better in general. Brown is gentler over long periods and masks low rumble more effectively; white covers speech more effectively because that is where its energy sits. Which one suits you is a preference, and it is worth trying both.
Is brown noise the same as red noise?
Yes, they are two names for the same minus 6 dB per octave slope. This site accepts either name, and the generator makes no distinction between them.
Why does brown noise sound louder on some speakers?
Because most of its energy is below 500 Hz, and small speakers and laptop drivers roll that range off sharply. On headphones or anything with a woofer you hear the full weight of it, and it will seem much louder at the same setting.