What Is White Noise?

White noise is random sound with equal power at every frequency. Here’s what that means, why it hides other sounds so well, and what it can and can’t do. Press play to hear it as you read.

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All 22 sounds: noise colors, nature, places and machines

Noise colors

Nature

Places

Machines

The short answer

White noise1 is a sound made of random vibrations spread evenly across every frequency we can hear, from deep bass to high treble. “White” comes from light: white light contains every color in equal measure, and white noise contains every frequency in equal measure. The result is the familiar shhh of an untuned radio.

Equal per hertz, not equal to the ear

White noise has the same power in each hertz. But there are far more hertz at the top of the range: the octave from 10,000 to 20,000 Hz is a hundred times wider than the octave from 100 to 200 Hz. So white noise puts most of its energy in the highs, where hearing is also most sensitive (equal-loudness contours2), and that’s why it sounds bright and hissy. The family of noise colors is summed up well in colors of noise3. Pink noise evens this out per octave and sounds more balanced; brown noise leans further toward the lows.

NoisePower per hertzPower per octaveSounds like
WhiteFlat+3 dB each octave upTV static, air from a vent
Pink−3 dB per octave (1/f)Equal in every octaveSteady rain, wind in trees
Brown−6 dB per octave (1/f²)−3 dB each octave upDistant waterfall, heavy surf
Blue+3 dB per octave+6 dB each octave upA fine, high hiss
Violet+6 dB per octave+9 dB each octave upA sharp, airy hiss

How white noise hides other sounds

Your hearing is better at noticing changes than steady levels. A door closing in a silent room is a big jump; in a room filled with steady noise, the same door is a small one. This is called auditory masking4. Because white noise covers every frequency, it masks a little of everything, and it’s especially strong in the speech range, which makes it good at covering voices.

What it’s used for

  • Sleep: to cover traffic, neighbors and household sounds. See white noise for sleep.
  • Focus: to cover office or household chatter. Some studies suggest it helps people who are easily distracted more than others. See white noise for studying.
  • Babies: widely used for naps, at a low volume and a distance from the crib.
  • Privacy: in therapists’ and doctors’ waiting rooms, to stop conversations carrying.
  • Tinnitus: sound therapy uses noise to make ringing less noticeable; talk to an audiologist.
  • Testing: engineers use it to test audio equipment and acoustics.

What it can’t do

White noise doesn’t remove sound; it adds sound. It won’t make a loud room quiet, and playing it loudly to drown out a very loud noise risks your hearing. It isn’t a treatment for insomnia, ADHD or tinnitus, though it’s a helpful tool for many people living with them.

Hear the difference

Sources

  1. Wikipedia. White noise. en.wikipedia.org.
  2. Wikipedia. Equal-loudness contour. en.wikipedia.org.
  3. Wikipedia. Colors of noise. en.wikipedia.org.
  4. Wikipedia. Auditory masking. en.wikipedia.org.

Questions

Why is it called white noise?

By analogy with white light, which contains all visible colors equally. White noise contains all audible frequencies equally.

Is white noise harmful?

Not at a low volume. Like any sound, it can damage hearing if it’s loud for long periods. Keep it quiet enough to talk over.

What’s the difference between white noise and pink noise?

White noise has equal power per hertz, which sounds bright. Pink noise has equal power per octave, which sounds softer and more natural.

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