Use the free White Noise Generator below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
Why a hiss helps you sleep
It sounds backwards. Adding noise to a bedroom should make sleep harder, not easier, and yet millions of people fall asleep faster with a steady hiss playing beside them. The reason is masking. A quiet room is not truly quiet: a door closes, a car passes, a pipe knocks, and each sudden sound stands out against the silence and wakes you. White noise fills the silence with a constant, even sound, so those sudden sounds no longer stand out. They are still there, but the gap between them and the background shrinks, and your brain stops treating each one as an alarm.
White noise is the most even masking sound available. It contains every frequency your ear can hear, all at equal strength, which is why it is called white, by analogy with white light containing every colour. That evenness is its strength: no matter what frequency a sudden sound has, the white noise already covers it. Pink and brown noise are softer and deeper, and many people prefer them, but when the goal is pure masking, such as in a noisy office or beside a busy road, white noise covers the widest range. Try it first if you have never used masking sound before, and switch to a deeper noise only if white noise feels too bright for you.
How this generator makes white noise
There is no recording and no audio file behind this tool. Your browser generates white noise live by filling a sound buffer with random numbers, one per audio sample, and looping that buffer through your speakers or headphones. Each random number becomes the height of the sound wave at one instant, and because the numbers are random, no frequency dominates, which is exactly the definition of white noise. The brightness slider runs the noise through a low-pass filter: at maximum it lets everything through, and as you lower it, the high frequencies fade and the hiss becomes duller and less sharp.
Generating the sound live has a practical advantage over playing a recording. A recording of white noise eventually repeats or, worse, contains a loop point you can learn to notice, which breaks the masking effect. A generated buffer, refreshed by the tool, has no recognisable pattern to learn, so your brain treats it as background and stops listening to it. That is the ideal outcome for a masking sound: present enough to cover interruptions, boring enough to ignore completely.
Focus, sleep, and babies: three different jobs
For focus, white noise works by covering the office sounds that pull your attention away: conversations, keyboards, phones. Set the volume just high enough that speech from across the room becomes hard to follow, but low enough that your own thinking stays clear. If the noise itself starts to distract you, lower the brightness slider rather than the volume: dulling the high frequencies often removes the distraction while keeping the masking. For sleep, start the noise before you get into bed, so the room already sounds the way it will sound all night, and use the sleep timer to stop it after you are asleep, or leave it running all night if you wake at small sounds.
Parents use white noise for babies for the same masking reason, and the same rules apply with extra care: keep the volume low, keep the source away from the cot, and prefer a dull, low setting over a bright, loud one. A baby’s hearing is sensitive, and the goal is a gentle background, not a wall of sound. Adults testing hearing sensitivity should also be careful: white noise at high volume for long periods is still noise exposure, and the volume slider exists so you can find the lowest level that does the masking job.
Getting the most from it
Use headphones for focus in shared spaces, and a speaker for sleep, so the sound fills the room the way real background sound does. Give yourself three nights before judging it for sleep: the first night with any new sound feels strange, and the benefit usually shows on the second or third night, once your brain has filed the hiss as background. If white noise feels too sharp, try the brightness slider first, and if it still feels wrong, the pink and brown noise generators on this site offer the same masking with a deeper, softer character. Nothing you do here is uploaded, and the sound stops when you press Stop or when the sleep timer ends.