White noise generator

White, pink, brown and green noise

All four are random sound with no rhythm or tune. What changes is how the energy is spread from low to high frequencies, which changes the character a lot:

• White noise has the same energy at every frequency. Our ears pick up a lot of detail in the high range, so it sounds like a bright hiss, like a radio between stations or air escaping a tyre.
• Pink noise has less energy as the frequency rises, with the same amount in each octave. It sounds softer and more even, a bit like steady rain.
• Brown noise drops off faster still, leaving mostly low frequencies. It’s a deep, soft rumble, like a waterfall heard from a distance or the inside of a plane. The name comes from Brownian motion, not the colour; it’s also called red noise.
• Green noise is pink noise focused on the middle of the range, around 500 Hz, with the deepest rumble and the brightest hiss taken out. It sounds like a steady stream or wind in trees.

If white sounds harsh to you, move to pink, and from pink to brown if you want something darker. Try green if pink has too much hiss and brown too much rumble. Each ear gets its own random sound, which feels more spacious on headphones than the same signal in both.

Getting a good night with it

• Set the sleep timer. Stop after 30 minutes or 1 hour covers falling asleep without hours of sound afterwards. The timer counts down under the controls and fades the sound out over a few seconds so the end doesn’t wake you.
• Keep the device awake. A computer that goes to sleep stops the sound. Plug a laptop in and check its power settings, or leave the timer at Never only if you mean to.
• Put the speaker across the room. Sound from a speaker a few metres away is gentler than sound right by your head, and you can keep the volume lower.
• Change the colour, not the volume. If the noise doesn’t cover a particular sound, try a different colour before turning it up. Brown covers low rumbles better; white covers higher, sharper sounds.