Why "Colours" of Noise?
The "colour" terminology borrows from optical physics: just as white light contains every visible wavelength, white noise contains every audible frequency at equal intensity. Different colours = different frequency weightings.
Three colours dominate the sleep & focus conversation: white, pink and brown. They differ not in what frequencies are present, but in how loud each frequency is relative to the others.
Choosing well matters: white noise can feel fatiguing over hours; brown noise can feel muffled when you actually want masking. The right colour depends on your goal, the room, and your own ears.
Quick Reference Table
| Colour | Sound | Spectrum | Best for | Avoid if |
|---|---|---|---|---|
| White | Bright hiss, like untuned TV static | Flat (equal energy) | Masking speech, ADHD focus, baby sleep | You find high frequencies fatiguing |
| Pink | Soft waterfall, balanced rain | −3 dB/oct (equal per octave) | Deep sleep, memory consolidation, natural feel | You need strong low-end masking |
| Brown | Deep rumble, distant thunder, low waterfall | −6 dB/oct (very bass-heavy) | Long focus sessions, low-frequency masking, anxiety | You're masking high-pitched sounds (alarms, voices) |
| Grey | Perceptually flat across human hearing | Psychoacoustically equal-loudness | Tinnitus retraining, hearing tests | You want a single dominant texture |
| Blue / Violet | Sharp, hissy, high-pitched | +3 / +6 dB/oct (treble-heavy) | Audio engineering tests, tinnitus therapy | Sleep — too harsh for relaxation |
| Black | Silence with sparse events; very deep drone | Mostly empty / sub-bass only | Light sleepers who dislike continuous sound | You need consistent masking |
When to Use Each Colour
White noise
Reach for white noise to mask sharp, intermittent sounds (chatty office, snoring partner). Strong evidence for use in NICU and infant sleep. Can feel hissy after an hour.
Pink noise
Closest to natural soundscapes (rain, wind). Papalambros et al. (2017) found pink noise played in phase with slow-wave sleep enhanced memory in older adults. A safe default for most people.
Brown noise
The deep, warm choice. Popular among ADHD adults for long focus sessions. Excellent for masking low traffic rumble and air-handling units. Less effective against high-frequency disturbances.
Grey noise
Engineered to sound equally loud at every frequency to the human ear. Used clinically in tinnitus retraining therapy. Less common in consumer apps.
Violet / blue noise
Treble-heavy and harsh. Niche uses: tinnitus masking at specific high frequencies, audio engineering test signals. Rarely used for sleep.
Black noise
An informal term — sometimes meaning near-silence, sometimes ultra-low-frequency drone. Useful for light sleepers who find any audible noise distracting but still want a "presence" in the room.
Sources & Further Reading
- Papalambros NA et al. (2017). Acoustic Enhancement of Sleep Slow Oscillations and Concomitant Memory Improvement in Older Adults. — Frontiers in Human Neuroscience
- Riedy SM et al. (2020). Noise as a sleep aid: A systematic review. — Sleep Medicine Reviews
- Söderlund GBW, Sikström S, Smart A (2007). Listen to the noise: noise is beneficial for cognitive performance in ADHD. — Journal of Child Psychology and Psychiatry
- Zhou J et al. (2012). Pink noise: effect on complexity synchronization of brain activity and sleep consolidation. — Journal of Theoretical Biology
This article is for educational purposes only and is not medical advice. Always consult a qualified healthcare professional for personal concerns.
Frequently Asked Questions
What's the difference between white, pink and brown noise?
Which noise is best for sleep?
Is brown noise better than white noise for focus?
What is black noise?
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