White noise generator

All three are random noise; they differ in how their energy is spread across frequencies.

Noise	Sound	Often used for
White	Bright hiss, like TV static or a fan	Masking speech and sharp sounds
Pink	Softer and deeper, like steady rain or a waterfall	Sleep and relaxation
Brown	Low rumble, like distant surf or an airplane cabin	Sleep, focus, masking low traffic hum

White noise has equal energy at every frequency, so to our ears it sounds bright. Pink noise drops 3 dB per octave and brown noise about 6 dB per octave, so more of their energy sits in the low frequencies. Which one is best is personal: try each for a few minutes.

Sudden sounds wake you or break your concentration because they stand out against silence. A steady background sound raises the baseline, so a door slam, a neighbor's TV or a barking dog is less of a jump. That is masking: the noise does not cancel other sounds, it makes them less noticeable.

Many people use noise in open-plan offices, while studying, in hotel rooms and in apartments with thin walls. Some find it helps them fall asleep faster; others prefer silence. It is worth testing for a few nights.

Choose Stop after 15, 30, 45, 60, 90 or 120 minutes. During the last 20 seconds the sound fades out gradually instead of cutting off abruptly, which is less likely to wake you. The timer runs on your device's audio clock, so it works in a background tab and, on most phones, with the screen locked, as long as the browser keeps playing audio.

To play all night, leave the timer off. The noise is generated as a seamless loop, so there is no audible gap or click.

Keep it quiet. For sleep, the noise only needs to be loud enough to blur other sounds, usually softer than a normal conversation. Long exposure to loud sound can damage hearing; the U.S. National Institute on Deafness and Other Communication Disorders notes that long or repeated exposure to sounds at or above 85 dBA can cause hearing loss.

For infants, pediatric researchers have found that some sound machines can get loud enough at full volume to be a concern, so keep the volume low. Place your phone or speaker across the room, not next to the baby's head, and use the timer. If you want to know how loud it actually is, check with the decibel meter from where the listener sleeps.

• Use a speaker rather than earbuds for sleep, so you are not lying on hardware all night.
• Plug in your phone if you play for hours.
• Turn on Do Not Disturb so notifications don't break the sound.
• If white noise feels harsh, switch to pink or brown; most people find the deeper colors easier to sleep with.

Everything is generated in your browser; there is nothing to download and no account to create.