White, brown or fan?
White noise vs brown noise (and fan noise)
White noise has the same power at every frequency, so it sounds bright and even, like a hiss. Brown noise loses about 6 dB of power for every octave up, so it sounds deep and soft, like a rumble. A fan is neither exactly: its motor and blades shape its sound. Fan Noise has all three, free.
The three, side by side
| White noise | Brown noise | Fan noise | |
|---|---|---|---|
| Sounds like | A bright, even hiss | A deep, soft rumble | A steady whoosh or hum |
| Its power across pitches | The same at every frequency | Falls about 6 dB per octave as the pitch rises | Shaped by the fan: its motor, its blades and how fast they turn |
| In Fan Noise | Free | Free | Nine fans, free, each at three speeds |
What the colours mean
A noise’s colour says how its power spreads across low and high pitches. White noise holds the same power at every frequency. Brown noise falls about 6 dB for every octave up, so its low end dominates; it’s named after Robert Brown, who described the random motion of particles it follows, not after the colour. Pink noise sits between them, falling about 3 dB per octave, and grey noise is shaped to sound equally loud at every pitch.
Is a fan white noise?
Not strictly. White noise spreads its power evenly across every frequency, while a fan’s sound comes from its motor and the air its blades push, so each fan sounds different and none is perfectly even. It does the same job, though: the Sleep Foundation calls a fan running at night “an easy, cost-effective source of white noise.”
Which is best for sleep?
Nobody can say for sure. A 2021 systematic review of 38 studies rated the evidence that continuous noise improves sleep as very low quality, so treat any promise with care. What matters more is the sound you like falling asleep to, at a volume that stays comfortable.
Try each for a night. If white noise sounds harsh, try brown; if you miss the hum of a fan, try the box fan.
All of them in one app
Fan Noise has nine fans and white and brown noise, free, with a sleep timer that fades them out. Fan Noise Plus adds pink and grey noise among its 46 more sounds, and a mixer that plays up to four at once, such as a fan with rain under it. See them all on the Fan Noise home page.
Questions, answered.
- What is the difference between white noise and brown noise?
- White noise has the same power at every frequency, so it sounds bright, like a hiss. Brown noise loses about 6 dB of power for every octave up, so its low frequencies dominate and it sounds deep, like a rumble.
- Is a fan white noise?
- Not strictly. White noise has equal power at every frequency, while a fan’s sound depends on its motor, its blades and its speed. It’s steady and broad like white noise, which is why many people use it the same way, to cover other sounds while they sleep.
- Is brown noise better than white noise for sleep?
- There’s no good evidence either way. A 2021 systematic review of 38 studies rated the evidence that continuous noise improves sleep as very low quality. Choose the one you find most restful, at a comfortable volume.
- What is pink noise?
- Noise whose power falls about 3 dB per octave, between white and brown, so it sounds softer than white noise and brighter than brown. In Fan Noise, pink and grey noise are part of Fan Noise Plus; white and brown noise are free.
Sources, checked
- Wikipedia: Colors of noise: white noise has a flat power spectrum; pink noise falls 3.01 dB per octave and brown noise 6.02 dB per octave; grey noise is weighted to an equal-loudness curve.
- Wikipedia: Brownian noise: “The term ‘Brown noise’ does not come from the color, but after Robert Brown”.
- Riedy, Smith, Rocha and Basner, Noise as a sleep aid: a systematic review, Sleep Medicine Reviews 55 (2021): 38 studies; “the quality of evidence for continuous noise improving sleep was very low”.
- Sleep Foundation: Is Sleeping With a Fan On a Good Idea? (updated August 21, 2025): “Leaving the fan running at night is an easy, cost-effective source of white noise”.