Short answer
The colour names are precise acoustic definitions, not marketing: white noise has equal power at every frequency, pink noise's power falls off as frequency rises, and brown noise falls off roughly twice as fast again, which is why it rumbles rather than hisses. The claims attached to them are not. No trial has compared them head to head for sleep, the evidence that any continuous noise improves sleep has been graded very low quality, and the best meta-analysis of noise and attention in ADHD found no studies of brown noise. Pick whichever you find least intrusive at a low volume: all three mask your alarm equally well, and none do anything for someone who is deaf or has significant hearing loss.
EIVOI sells a white noise machine, disclosed up front. If the honest answer is that the colour barely matters, that is the answer, including for the colour we sell.
What the colours actually mean
The names describe the shape of a signal's power spectrum: how its energy is distributed across frequency. None of this is vague or disputed, and a spectrum analyser app will confirm it.
White noise has a flat power spectral density: equal power in every equally wide slice of the range, so 100 to 200 Hz carries as much as 5,000 to 5,100 Hz. Human hearing groups frequencies logarithmically rather than linearly, so a flat spectrum sounds top-heavy. White noise is the hissy one.
Pink noise has power proportional to 1/f, a fall of about 3 dB per octave. Each octave then carries the same power as the next, so 100 to 200 Hz matches 1,000 to 2,000 Hz. That is closer to how hearing is organised, which is why pink sounds more balanced and rain-like.
Brown noise has power proportional to 1/f², a fall of about 6 dB per octave. Almost all the energy sits at the bottom, so it reads as a waterfall or distant thunder. It is named after Brownian motion, not the colour.
These labels are not regulated in products, though: a track titled "brown noise" need not have a 1/f² spectrum, so two people arguing about it may not be discussing the same signal.
Precise definitions do not make the sleep claims precise
Knowing what pink noise is tells you nothing about whether it helps you sleep. Separate questions, and the second is in poor shape.
The reference point is the systematic review by Riedy, Smith, Rocha and Basner in Sleep Medicine Reviews in 2021, which pooled 38 studies of noise as a sleep aid and graded the evidence that continuous noise improves sleep as very low quality. That review, and the 2026 study from Mathias Basner's group at the University of Pennsylvania associating pink noise with less REM sleep, are covered on our white noise machine page.
The point specific to this page is narrower. If the evidence for noise in general is weak, the evidence comparing colours is weaker still, because barely anyone has run that comparison. The 2021 review named heterogeneity in the sound used as one reason its studies could not be pooled cleanly, and heterogeneity is what you get instead of a head-to-head trial, not a substitute for one. The studies that exist are small and point different ways: Zhou and colleagues reported in the Journal of Theoretical Biology in 2012 that steady pink noise increased stable sleep time, while Vickrey and Lerner, in Frontiers in Human Neuroscience in 2023, found that people who slept with pink noise performed more like those who had stayed awake on a pattern-detection task.
One confusion feeds much of the confident writing. The research showing that sound can deepen slow-wave sleep, starting with Ngo, Martinetz, Born and Mölle in Neuron in 2013, used millisecond bursts timed to each slow oscillation by a lab system reading the sleeper's EEG. Those bursts happen to be pink noise. A machine playing it continuously is not a budget version.
Brown noise and ADHD: what is actually behind it
The research tradition is real, and it starts with white noise, not brown. Söderlund, Sikström and Smart published "Listen to the noise: noise is beneficial for cognitive performance in ADHD" in the Journal of Child Psychology and Psychiatry in 2007, finding that white noise improved performance in children with ADHD while worsening it in controls. Their explanation was stochastic resonance, later formalised as the Moderate Brain Arousal model: differences in dopamine signalling leave people with different optimal levels of background stimulation.
The best current summary is the systematic review and meta-analysis by Nigg, Bruton, Kozlowski, Johnstone and Karalunas in the Journal of the American Academy of Child and Adolescent Psychiatry in 2024. Pooling 13 studies covering 335 young people with ADHD or elevated attention problems, they found a small but statistically significant benefit of white or pink noise on task performance, a pooled effect size around 0.25, alongside a small negative effect in the non-ADHD comparison groups. They called for further work to confirm it and establish safe sound levels.
The part that matters: those authors state plainly that they identified no studies of brown noise. The colour with the loudest reputation has the least research behind it, and what exists for the neighbouring colours is small, preliminary, and about task performance while awake rather than sleep. The model is contested as well. Jostrup and colleagues tested 97 children in the Journal of Attention Disorders in 2024 and found that neither auditory nor visual white noise helped either group. Cleveland Clinic's write-up quotes its own physician saying the trend runs mainly on social media testimonials.
Two things this page will not do. It will not tell you whether you have ADHD, which is a clinical assessment and not something inferable from whether a sound feels good. And it will not present any colour of noise as a treatment for it. If concentration difficulties are affecting your daily functioning, that belongs with a clinician. ADHD and oversleeping covers the sleep-side questions.