Brown Noise — Free Online Generator
Brown noise is the deepest of the three classic noise colors — a rolling, bass-heavy sound that masks low-frequency disturbances and feels closer to ocean surf or a distant freight train than to static. NoiseMoon generates it procedurally in your browser. No file loop. No upsell. Works offline once installed.
What is brown noise?
Brown noise is a random signal whose power spectrum decreases by 6 decibels per octave as frequency rises. The name comes from Brownian motion — the same random-walk process the noise resembles — not from the color brown. Compared to the more familiar white noise (flat across all frequencies) and pink noise (−3 dB/oct), brown noise puts most of its energy at the bottom end. It sounds darker, smoother, and more like a sustained low rumble than a hiss. Headphone listeners often describe it as "filling the room from underneath."
What brown noise does
Brown noise tends to mask low-frequency environmental sounds — HVAC rumble, distant traffic, partner snoring, footsteps from the floor above. It's especially effective when the disturbance you're trying to ignore lives in the bottom two octaves of human hearing, which is exactly where most household and street noise concentrates. Brown noise is not a treatment. Some people prefer its low-frequency balance for focus; others do not. The same goes for sleep: some listeners find the smoother spectrum more comfortable than the brighter hiss of white noise, and some don't — choose whatever feels right to your ears.
How to use it
Start at a low, comfortable volume. Use the warm ↔ bright slider to taste; full warm gives you the deepest, most rumble-like tone. The Spaceship preset (selected by default on this page) is calibrated to match the spectral shape of the most popular brown noise tracks online — about −12 dB/octave, which is darker than textbook brown but is what most modern listeners actually mean when they search for "brown noise." If you want pure mathematical brown noise, switch to the Cabin or another preset and dial the warm slider toward bright. Headphones or a speaker both work — pick whichever is more comfortable for the session.
Try it in NoiseMoon
Brown noise is not a treatment. Some people prefer its low-frequency balance for focus; others do not — response is individual. In NoiseMoon you can hear the difference for yourself: the Spaceship preset gives you the popular extra-dark shape, other presets sit closer to textbook brown, the warm ↔ bright slider tilts the spectrum in real time, and the timer fades the sound out on your schedule. NoiseMoon is not medical advice — consult a clinician for clinical questions.
Frequently asked
Is brown noise safe to listen to all night?
Treat it like any other audio: keep the volume at a comfortable level. NoiseMoon's procedural generation has no loop seam, and the built-in timer can fade the sound out on your schedule.
What's the difference between brown noise and pink noise?
Brown noise rolls off at −6 dB per octave (twice as steep as pink), making it noticeably darker and bass-heavy. Pink noise rolls off at −3 dB/oct and sounds more like steady rainfall. Brown is closer to low rumble or distant traffic; pink is closer to a fountain.
Does brown noise really help with ADHD?
Brown noise is not a treatment. Some people prefer its low-frequency balance for focus; others do not.
Can I use brown noise for a baby's sleep?
NoiseMoon is not medical advice. If you use sound for a baby, use the lowest comfortable level, keep the device away from the baby, and ask a pediatrician or care team for individualized guidance.
Why does NoiseMoon's brown noise sound different from YouTube videos?
Most popular YouTube "brown noise" tracks are looped audio with extra low-pass filtering applied — closer to −12 dB/oct than textbook −6. NoiseMoon offers both: the Spaceship preset matches that popular dark-brown sound, while you can dial down to pure mathematical brown via the warm/bright slider.
Does NoiseMoon work offline?
Yes. Add NoiseMoon to your home screen (PWA install) and the entire app runs offline — no streaming, no buffering. The noise is generated mathematically on your device, sample by sample.