Green noise is noise turned down at the low and high ends of what people can hear, leaving a wide band centered around 500 Hz — built live in your browser as white noise sent through a band-pass filter, which gives it a rounder, steadier character than a plain hiss.
Is green noise a real color of noise?
Not in the way white, pink and brown are. Those three names come from settled definitions in acoustics and engineering, each with a formula for how its energy is spread across frequency. "Green noise" has no single agreed definition — different apps and sites mean somewhat different things by it, and there's no standards body deciding between them. What greensound builds under that name is the filtered signal described above, nothing more.
Green noise or brown noise?
Brown noise, on greensound, doesn't use a filter node. Its low weighting comes from a running sum computed sample by sample inside the audio worklet itself — each new value nudges the last one, then leaks back toward zero — which behaves like a one-pole low-pass, built in code rather than with a separate filter node. Green noise instead runs through an actual band-pass filter node, turned down at both ends around its center. The two land in different parts of the range, and they're built by genuinely different means, not two strengths of one process.
Green noise or white noise?
White noise, on this site, is plain random samples with nothing shaping them afterward: one random value per sample, spread evenly across the whole range you can hear. Green noise starts from that same kind of raw random signal and runs it through a band-pass filter centered at 500 Hz — a wide one, so a fair amount still comes through well beyond the center; at 5 kHz, about three octaves up, the level is only about 17 dB down, not silenced. Next to unfiltered white noise, green noise still reads as rounder and less bright, since its harsher top end is turned down rather than removed outright.
Does it ever repeat?
No. It's generated one audio sample at a time by code running continuously on your device for as long as the channel plays — there's no fixed-length clip looping underneath it, and so no loop point for a seam to appear at, however long a session runs.
Where the sound comes from
Green noise. Made in your browser, not a recording.
Listen safely
This is a sound, played back through whatever speaker or headphones you already own. It doesn't diagnose, measure, or promise anything about how you sleep, focus, or feel — it's just noise and a handful of real recordings, mixed the way you like them.
Keep the volume low enough that you'd still notice a smoke alarm, a phone ringing, or someone at the door. If you fall asleep in headphones, choose a volume and a pair you'd be comfortable wearing all night, and a session length that ends when you'd want the sound to stop.
If you use this near a baby, keep the speaker several feet from the crib, never inside or clipped to it, and keep the volume low — the same care you'd take with any sound machine in a nursery.
If your relationship with sound, or with sleep, feels difficult rather than simply restless, a doctor or audiologist is the right person to talk to. This is a mixer, not a clinician.
What is green noise, exactly?
+
It's noise with more energy in the middle of the audible range and less at the very top and bottom. White noise spreads its energy evenly across every frequency you can hear, which is why it sounds thinner and more hissy by comparison.
Is green noise a recording of something real?
+
No. It's generated live by your browser from mathematical noise, the same way white and brown noise are. Nothing about it is a field recording, and it never claims to be — the real recordings on this site are marked with where they were recorded.
Can I run green noise at the same time as a real recording?
+
With Pro, yes. The mixer supports up to six sounds at once, each with its own volume, so green noise can sit under night wetland, beach waves or any other sound here. Without Pro, one sound plays at a time.
What volume should I use?
+
Quiet enough that you could hold a conversation over it without raising your voice. Noise that's loud enough to fully mask other sound in a room is louder than most people need.
Is green noise part of the free plan?
+
Yes, fifteen minutes a day. This sound is free to play for fifteen minutes a day, with a fade at the end, and Pause keeps the minutes you have left. Pro adds the full mixes, layering, longer timers, and new recordings first.