White, pink, brown, and violet noise — which one for sleep?

"Noise colors" sound like marketing — they're not. Each color is a specific spectral shape, defined by how much power sits at each frequency. The differences are real, audible, and the research is solid enough to make reasonable picks. Here's the plain-English version.

What "color" actually means

The color names come from analogy with light. White light has equal power across all visible wavelengths; white noise has equal power across all audible frequencies. The other colors shift that balance:

White

Equal power per frequency. To human ears it sounds bright, almost hissy — because we hear higher frequencies as louder per unit power.

Pink (1/f)

Power decreases with frequency. Naturally balanced to how human hearing perceives loudness. Sounds like steady rain or wind. The most-cited noise color in sleep research.

Brown (1/f², a.k.a. "red")

Power decreases faster with frequency — much more bass. Sounds like a distant waterfall or ocean roar. Substantial ADHD-community following in the last few years.

Violet (f²)

Power increases with frequency. Very bright, hiss-heavy. Used for hearing tests, audiometric calibration, tinnitus masking. Almost no one falls asleep to this.

Green (narrow-band, ~500 Hz)

Not strictly a "color" — a single band of noise concentrated near the middle of human hearing. Newer; sometimes used in tinnitus-masking research.

What the research actually says

The sleep-and-noise literature is dominated by white and pink. A few patterns hold up across studies:

• Continuous broadband noise (white, pink, or brown) reduces sleep-onset latency more than silence in noisy environments. Magnitude varies; effect is consistent.
• Pink noise specifically has some evidence for improving slow-wave sleep depth in older adults. See Papalambros et al. (2017) — a small but well-cited study using phase-locked pink-noise pulses during deep sleep. Generalization to "just play pink noise all night" is shakier.
• White noise is more arousing than pink for many listeners. The treble-weighted spectrum sits in the same range as sudden environmental sounds, so the masking trade-off is worse.
• Brown noise's recent popularity is mostly anecdotal. The ADHD community has discovered brown noise as a focus/sleep aid in the last few years; published research on brown specifically is sparse. The mechanism — bass-weighting feels less "loud" per unit perceived volume — is plausible.

How to pick

If you're trying to choose without any other context:

1. Start with pink. Balanced spectrum, most-studied, most-tolerated. If pink works, you're done.
2. Switch to brown if pink feels too "hissy" or treble-heavy. Common preference for ADHD listeners or anyone bothered by the treble end.
3. Try white only if pink and brown both don't mask the specific intrusion you're worried about. White is the most masking but most arousing.
4. Skip violet for sleep. It's a tool for tinnitus testing, not for falling asleep.
5. Use narrow-band green if you have tinnitus. Some tinnitus-masking clinicians recommend a narrow band tuned just away from the tinnitus frequency; talk to an audiologist about specifics.

Pink + brown wash — the underused option

Most consumer white-noise machines only ship one noise type. A pink + brown blend is a useful sleep target — pink fills in the high-mid range, brown fills in the bass — but it requires either two machines or a synth that can mix them. Sleep Sine's Deep Space scene does this (the noise synthesis mode mixes pink, brown, narrow-band green, and binaural at independently-tunable levels). The Pink + Brown Wash preset in that scene's gallery is exactly this configuration.

What about "binaural beats"?

Different from noise colors. Binaural beats present a slightly different frequency in each ear; the brain perceives the difference frequency. Some research suggests modest sleep-onset benefits at specific difference frequencies (delta or theta range). Other research finds no measurable effect. Requires headphones — speakers don't produce the perceived beat. Try it if you sleep with headphones; ignore it otherwise.

Selected sources: Papalambros et al. (2017) — phase-locked pink noise + slow-wave sleep in older adults. Capezuti et al. (2018) systematic review of sound-based sleep interventions. ADHD/brown-noise content is mostly anecdotal; published research is in progress.