How it works
The noise is synthesised with the Web Audio API: random samples make white noise; a set of filters tilts the spectrum by −3 dB per octave for pink noise; and integrating the random signal gives brown (red) noise, which falls by −6 dB per octave. An 8-second stereo buffer is looped with a cross-fade, so there is no click and the left and right channels are independent.
The level is lowered for white and raised for brown noise so that the three colours sound about equally loud. The volume slider follows a squared curve for finer control at low levels, and the sleep timer can fade the sound out over the last minute instead of cutting it off.
White, pink and brown noise
| Colour | Spectrum | Sounds like |
|---|---|---|
| White | Equal power at every frequency (flat) | Bright hiss, like an untuned radio |
| Pink | Equal power in every octave (−3 dB per octave) | Softer, like steady rain |
| Brown | Power falls with the square of frequency (−6 dB per octave) | Deep rumble, like a waterfall or distant surf |
Steady noise does not make a room quiet; it masks changing sounds such as traffic or voices so they stand out less. Which colour feels best is personal, and research on sleep benefits is mixed.
Tips
- Start quiet and raise the volume only until distracting sounds blend in. For sleep, the speaker should not be right next to your head.
- Use the timer at night so the sound does not play for the whole night unless you want it to.
- For focus, pink or brown noise is usually less tiring than white noise over long periods.
Standards and sources
- Web Audio API · W3C Recommendation
- AudioBuffer · MDN Web Docs
- Make Listening Safe initiative · World Health Organization
Last reviewed October 18, 2026
Frequently asked questions
What is the difference between white, pink and brown noise?
They differ in how the sound energy is spread. White noise has equal power at all frequencies and sounds bright; pink noise has equal power per octave and sounds softer; brown noise is weighted towards low frequencies and sounds deep.
Is it safe to sleep with noise on?
Keep the volume low, only loud enough to mask other sounds, and use the timer. Long exposure to loud sound can damage hearing; the World Health Organization’s safe-listening work explains the risks.
Does it work offline and in the background?
The noise is generated on your device, so it keeps playing without a connection once the page is open. Some phones pause web audio when the screen locks or the browser goes to the background.