Learn · Noise colours
White, pink and brown noise.
White, pink and brown noise are random signals that differ only in how their power is spread across frequencies. White noise has equal power at every frequency, pink noise loses 3 dB per octave, and brown noise loses 6 dB per octave, so each sounds deeper than the one before.
Raumo offers all three as optional sounds of its room. It makes no claim about what any of them does.
Updated
By spectrum
Every noise is a random signal: no two moments are the same, but its average distribution of power across frequencies, its spectrum, stays the same. The colour names describe that spectrum, by analogy with light.
| Noise | Power per hertz | Power per octave | How it sounds |
|---|---|---|---|
| White | Equal at every frequency (flat) | Rises 3 dB per octave | Bright and hissy, like a detuned radio |
| Pink | Falls 3 dB per octave (1/f) | Equal in every octave | Fuller and softer, like steady rain |
| Brown | Falls 6 dB per octave (1/f²) | Falls 3 dB per octave | Deep and rumbling, like a distant waterfall |
Each colour
White noise
White noise has the same power in every hertz of its range, the way white light contains all visible colours. Because each octave up spans twice as many hertz as the one below, most of its energy lies in the high frequencies, which is why it sounds bright. Digitally it is simply a stream of independent random samples.
Pink noise
Pink noise has equal power in every octave: as much between 100 and 200 Hz as between 1,000 and 2,000 Hz. Its power per hertz falls in proportion to 1/f, about 3 dB per octave. Because hearing also groups pitch in octaves, pink noise sounds more even across its range than white. It is the usual test signal for measuring rooms and loudspeakers.
Brown noise
Brown noise, also called Brownian or red noise, is named after Brownian motion, not the colour: it is what you get by adding up white noise step by step, a random walk. Its power per hertz falls as 1/f², 6 dB per octave, so it is mostly low rumble with little hiss.
Other noises
Grey noise is shaped to sound equally loud at all frequencies, following the ear’s equal-loudness contours. Blue and violet noise rise with frequency, the opposite of pink and brown, and are used mainly in audio and image processing.
Noise in Raumo
In Raumo, noise is one of the sounds you can add to a room. White, pink and brown noise are generated live by the app as you listen, not played from a file. Like any sound of the room, a noise has a place: bring it closer and it becomes louder, move it to the edge and it fades to silence. It takes a little of the room’s reverb, and no echo.
Besides the three colours, the Noise family has grey noise, warm noise, deep brown, a slowly breathing noise, a fan, and three bands centred on 250 Hz, 1 kHz and 4 kHz. Tape textures, such as cassette hiss and vinyl dust, are a family of their own. The Noise & Tape playlist plays textures without music, and noise can sit under any soundscape.
Raumo makes no claim that any noise helps sleep, focus, mood or health. These are sounds to choose, described here by their physics.
Hear the difference
Recordings of Raumo’s audio engine: each noise alone, without music, straight ahead of the listener in a soundscape’s room, recorded with the app’s headphone rendering. Their levels are as the engine produced them at the same place, so white noise, whose energy lies mostly in the softened highs, is the quietest. Headphones show the difference best.
White noise
Pink noise
Brown noise
