Decibel Shield
White noise generator › Green noise
Green noise generator
Green noise is noise concentrated in the middle of the range, around 500 Hz, with the deep rumble and the high hiss taken out, so it sounds soft and enclosed, like a distant waterfall. Press play to generate it in your browser, with nothing downloaded and no account, set a sleep timer up to eight hours, and measure how loud it really is.
The middle of the range with the deep rumble and the hiss taken out. An informal sleep-app name, not an acoustics standard.
How loud is this actually?
The slider sets digital volume, which is not a decibel level — what reaches your ear depends on your device and speakers, so no website can know it. This one can measure it, because measuring is what the rest of this site does.
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Green, pink, brown and white noise compared
Most noise colours are a slope across the whole range. Green is different: it is a band, the middle of the range with both ends rolled off. It is an informal name from sleep apps rather than an acoustics term, so this page says exactly how it is made: white noise through a wide band-pass centred on 500 Hz. The white noise generator has all seven colours; pink and brown noise have their own pages.
| Colour | Shape | What it sounds like |
|---|---|---|
| Green | centred near 500 Hz | The middle of the range with the deep rumble and the hiss taken out. An informal sleep-app name, not an acoustics standard. |
| Pink | −3 dB/octave | Equal power per octave, so it sounds balanced rather than bright. Steady rain. |
| Brown | −6 dB/octave | Weighted to the low end. A waterfall, or a jet heard from inside the cabin. |
| White | 0 dB/octave | Equal power at every frequency. The bright, even hiss of an untuned radio. |
Volume is not a decibel level
The slider sets digital volume. What reaches your ear depends on your phone, your speaker and how far away it is, so no website can know it. The measure button reads the room with the same maths as the decibel meter on this site; the safe decibel levels page has the limits. A sleep sound should sit far below them.
Questions
What is green noise?
Noise that emphasises the middle of the audible range, often described as centred around 500 Hz, with less of the deep rumble of brown noise and less of the hiss of white. It is an informal name from sleep and relaxation apps, not an acoustics standard (the US federal telecommunications glossary defines white, pink and blue noise, but not green), so different apps make it slightly differently. Here it is white noise through a wide band-pass at 500 Hz.
Green noise or pink noise: what is the difference?
Pink noise covers the whole range, tilted down 3 dB per octave so it sounds balanced. Green noise keeps only the middle: it drops the lowest bass and the highest treble, so it sounds softer and more enclosed, like a distant waterfall rather than rain on a roof.
Is green noise good for sleep?
There is little research on it either way, so nobody can promise a benefit. Some people find the missing hiss restful and the missing rumble less heavy than brown noise; others prefer a colour that covers more of the range, because traffic and voices sit both above and below the green band. The useful test is which one you stop noticing.
Does this download anything while it plays?
No. The noise is generated in your browser from a random source, so nothing is downloaded while it plays and it keeps working if your connection drops.
How loud should it be?
Quieter than most people set it. A website cannot know the level at your ear, so measure it with the button on this page. NIOSH puts the occupational limit at 85 dB averaged over 8 hours, and a sleep sound should be far below that.
Sources: Sleep Foundation, noise colours and sleep; Colors of noise, which lists green among the informal definitions.