Brown noise generator
A deep rumble, like distant surf. Best at covering traffic and bass. Generated live — no loop, no download.
Brown noise
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A free browser brown noise generator. Brown noise concentrates almost all of its energy in the low frequencies, which makes it the best of the three noise colours at masking traffic, bass, and machinery. This player synthesises it in real time by integrating white noise, the same method the Android app uses.
What brown noise is
Brown noise has a power spectral density proportional to 1/f², falling about 6 dB for every doubling of frequency. That is twice the slope of pink noise, and it is steep enough that by the time you reach the top of the audible range there is very little left.
The name is a genuine oddity. White and pink are named by analogy with light; brown is named after Robert Brown, the botanist whose observation of pollen jittering in water gave Brownian motion its name. The spectrum is what a random walk produces, and generating brown noise really is a matter of taking random steps and tracking where you end up. It is also called red noise, which at least keeps the colour metaphor intact.
What it is good at
Brown noise is the specialist of the three, and its specialty is low frequencies.
The sounds people most often want to escape at home are low: traffic, a neighbour’s music through a wall (bass passes through walls; treble does not), an air conditioner, a lift motor, building plant. Masking works by raising the background level in the same part of the spectrum as the intrusion, so the tool has to have energy where the problem is. Brown noise does; white noise, spread thin across a much wider range, does not.
It is also the easiest of the three to leave on for a long time. There is no hiss to fatigue against, which is why it dominates the “noise for concentration” recommendations that circulate online.
Where it falls short
The mirror image of its strength: brown noise is poor at masking speech. Voices live mostly above where brown noise has meaningful energy, so a conversation in the next room will cut through it in a way it would not cut through white noise. If the thing bothering you is people talking, brown is the wrong choice regardless of how pleasant it is.
There is one practical caution. Because brown noise never sounds harsh, it is unusually easy to run it louder than you intended — the signal that normally tells you to turn something down is absent. Set the level by whether you could hold a conversation over it, not by how comfortable it feels.
How this generator makes it
Brown noise is the simplest of the three to synthesise and the most delicate to get right.
Each output sample is the previous one plus a small random step — the random walk — divided by a factor slightly greater than one. That division is the important part. A pure random walk drifts: with nothing pulling it back, the signal wanders away from zero and eventually clips, which is audible as the sound distorting after a minute or two. Leaking a small fraction of the accumulated value on every sample keeps it centred indefinitely while leaving the spectrum intact.
The result is then scaled back up, because that leak costs amplitude. These are the same constants the Android app uses, carried over from the reference implementation both were ported from, so the browser and the app produce identical sound.
Because the integrator’s state carries continuously across audio blocks, there is no seam anywhere — this is also why brown noise in particular sounds wrong when it is looped from a recording, since the loop point lands mid-walk and produces an audible click.
Brown, pink, or white
Brown for rumble, traffic, bass, and long focus sessions. Pink when brown feels too dark but white feels too bright. White when the problem is voices. Switch between them with the swatches under the button — playback continues through the change, so you can judge them against the actual noise in your room.
Which noise should you use?
| Noise | What it sounds like | Energy per octave | Commonly used for |
|---|---|---|---|
| White noise | A flat hiss, like an untuned radio | Rises 3 dB per octave | Masking speech and sudden noises |
| Pink noise | Softer hiss, like steady rain | Flat across octaves | Sleeping and long listening sessions |
| Brown noise | A deep rumble, like distant surf | Falls 3 dB per octave | Blocking low-frequency noise and focus |
Take it offline
The same noise, on Android
One button, background playback, lock screen controls, and a home screen widget. No ads, no account, no subscription.
- Pay once, keep it forever
- No ads and no tracking inside the app
- No internet permission — it works fully offline
- Keeps playing when the screen is off
- Home screen widget and lock screen controls
- Plays on Wear OS watches on their own
One-time purchase, about $0.20. Price varies by country.
Questions
What is brown noise?
Brown noise is a sound whose power falls with the square of frequency, dropping about 6 dB per octave. That steep roll-off leaves almost all of its energy at the bottom of the audible range, producing a deep rumble rather than a hiss.
What does brown noise sound like?
Distant surf, a waterfall heard from below, heavy rain on a roof, or the inside of an aircraft cabin at cruise. It is the deepest and softest-seeming of the three noise colours, with none of white noise's hiss.
Why is it called brown noise if it is not a colour?
Because it is named after Robert Brown, not after the colour. Brown noise is the spectrum you get from Brownian motion — a random walk — which is exactly how it is generated. It is also called red noise, by analogy with the other colours, and that name at least fits the pattern.
Is brown noise good for focus?
It is the colour most often chosen for concentration, largely because it masks low-frequency distractions without adding a hiss of its own. Whether background noise helps focus at all is genuinely individual — some people work better with it and some measurably worse. It costs nothing to test on yourself.
Does brown noise block traffic and neighbours?
Better than white or pink noise, yes. Traffic rumble, a neighbour's bass, machinery, and building services all sit low in the frequency range, which is precisely where brown noise puts its energy. Masking works by raising the background level in the same band as the intrusion, so matching the two is what matters.
Is brown noise safe to listen to for a long time?
At a low volume, it is like any other quiet background sound. The thing to watch is level rather than colour: because brown noise has no harshness, it is easy to turn it up further than you would white noise without noticing. Keep it quiet enough to talk over, especially through headphones and especially overnight.