What are noise colors?
Just as white light contains all wavelengths of visible light combined, white noise contains all audible frequencies at equal intensity. When you reduce energy at higher frequencies — similar to filtering out blue light — you get warmer, lower-pitched noise. This analogy with the visible light spectrum gave rise to the "noise color" naming convention.
Each noise color is defined by its power spectral density — how much energy it has at each frequency. A flat spectrum produces white noise. A spectrum that decreases by 3 dB per octave produces pink noise. Decrease by 6 dB per octave and you get brown noise. Increase by 3 dB per octave and you get blue noise.
| Color | Slope | Character | Best for |
|---|---|---|---|
| ⬜ White | 0 dB/octave (flat) | Sharp, even hiss — like static | Masking, offices, infant sleep |
| 🌸 Pink | −3 dB/octave | Balanced, natural — like rainfall | Sleep, creativity, memory |
| 🟫 Brown/Red | −6 dB/octave | Deep, warm rumble — like a waterfall | Deep work, ADHD, anxiety |
| 🔘 Grey | Equal loudness curve | Neutral — flat to human perception | Tinnitus, long sessions, audiophiles |
| 🔵 Blue | +3 dB/octave | Bright, hissy — like air escaping | Audio dithering, less common |
| 🟣 Violet | +6 dB/octave | Very sharp, extreme treble | High-freq tinnitus masking |
| 🟢 Green | Centred ~500 Hz | Midrange focused — "nature" quality | Background ambience |
| ⬛ Black | Mostly silence | Silence with rare random bursts | Theoretical, not for listening |
White noise
White Noise
White noise is the reference standard. Every frequency from 20 Hz to 20,000 Hz is represented at the same energy level. To your ears it sounds bright and sharp — often described as a fan, a television set to a dead channel, or rushing air through a vent.
Because it covers the full frequency spectrum equally, white noise provides the most complete acoustic masking of any noise color. Any frequency your environment might throw at you — a slamming door, a dog barking, traffic, conversation — is already covered by the white noise layer.
The drawback: The high-frequency content that makes white noise effective also makes it feel harsh or fatiguing for some people over long sessions. If white noise irritates you, try pink or brown noise.
Pink noise
Pink Noise
Pink noise sits between white and brown — its energy decreases by 3 dB for every doubling of frequency. This means each octave band (20–40 Hz, 40–80 Hz, 80–160 Hz, etc.) contains the same total energy, which matches how human hearing perceives equal loudness across octaves. Pink noise sounds the most "natural" of the pure noise types — like steady rainfall, a moderate waterfall, or wind through leaves.
Pink noise has the most research support for sleep applications. A landmark Northwestern University study found that pink noise synchronized to slow-wave sleep oscillations improved deep sleep quality and next-day memory by 25%. Pink noise also appears in self-similar patterns throughout nature — the noise of ocean surf, heartbeats, brain activity, and even stock market fluctuations all approximate pink noise spectra.
Brown noise (Red noise)
Brown Noise / Red Noise
Brown noise — sometimes called red noise — has a much steeper high-frequency rolloff than pink noise. The result is a deep, warm bass rumble with very little treble content. It sounds like a powerful waterfall from a distance, a strong wind across a microphone, or the low roar of a large engine heard through walls.
Despite the name, brown noise has nothing to do with the color brown — it's named after the botanist Robert Brown, whose 1827 observations of random particle motion (Brownian motion) describes the mathematical process that generates this type of noise. "Red noise" is used interchangeably.
Brown noise has surged in popularity due to viral TikTok reports from ADHD users who find it silences mental chatter and enables deep focus. Its deep bass character also appears to have anxiolytic (anxiety-reducing) properties for many listeners.
Grey noise
Grey Noise
Grey noise is white noise that has been psychoacoustically equalized. Human hearing is not flat — we're far more sensitive to mid-range frequencies (1–4 kHz) than to very high or very low frequencies. White noise therefore sounds brighter than "equal" to our ears.
Grey noise compensates for this by applying the inverse of the equal-loudness contour — boosting frequencies we hear poorly and cutting frequencies we hear well. The result is a noise that sounds perceptually flat — genuinely equal across the spectrum as experienced by the listener. Most people describe grey noise as "white noise with the edge taken off."
Blue noise
Blue Noise (Azure Noise)
Blue noise increases in energy as frequency rises — the opposite of pink noise. It sounds very bright, hissy, and sharp — like air escaping through a narrow gap or the sizzle of a high-frequency audio cable. For most listening purposes, blue noise is uncomfortably bright and fatiguing.
Blue noise has practical applications in digital audio engineering — specifically in dithering, where it's used to add shaped noise to digital audio to reduce quantisation distortion in a perceptually optimal way. For sleep, focus, or relaxation, blue noise is rarely the right choice.
Violet noise (Purple noise)
Violet Noise / Purple Noise
Violet noise increases even more steeply than blue noise — 6 dB per octave. It sounds extremely bright, thin, and sharp — most listeners find it unpleasant for general use. The very high-frequency emphasis makes it effectively inaudible at the low end.
Violet noise has one specific therapeutic application: masking high-frequency tinnitus. Because high-pitched tinnitus (typically above 6,000 Hz) is not well-covered by white or pink noise, violet noise's emphasis of the upper frequency range can provide more efficient masking at lower overall volumes.
Green noise
Green Noise
Green noise is centred at approximately 500 Hz — the midpoint of the audible spectrum — and falls off on either side. It's sometimes described as the "colour of nature" because the ambient sound of natural environments (forest, meadow, gentle wind) tends to cluster around this frequency range.
Green noise is less standardised than white, pink, or brown — different sources define it slightly differently. It's a pleasant, mid-range focused sound that many people find the most comfortable for extended background listening. Less commonly available in standard generators but worth trying for those who find white noise too bright and brown noise too deep.
Which noise color should you use?
The honest answer is: whichever one you find yourself forgetting about within five minutes of starting it. The best background noise is the one you stop noticing — because you're focused on your work, or drifting off to sleep, rather than attending to the sound itself.
That said, here are the practical defaults based on the research and user experience:
- Starting from scratch? Try white noise first — it's the most studied and provides the broadest masking.
- White noise feels harsh? Switch to pink noise. It's often the sweet spot between effectiveness and comfort.
- Have ADHD or anxiety? Try brown noise specifically — it has the strongest community evidence for mental chatter reduction.
- Tinnitus? Start with white noise, consider grey noise for long-term use, and violet noise only if your tinnitus is in the very high frequency range.
- Want the most natural sound? Pink or green noise, or pair any noise color with nature sounds (rain, ocean, forest) from our generator.
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