Brown noise, white noise, or pink noise: which is best for focus?

Search for "brown noise" and you will find two things: a wave of people saying it switched their brain off for the first time in years, and almost no science about brown noise specifically. Both are true. This article explains what the colours of noise are, what has actually been measured, and how to choose one without pretending the evidence is stronger than it is.

The three colours, in one paragraph each

White noise has equal energy at every frequency. It sounds like a detuned radio or a hard hiss. Because human hearing is most sensitive in the middle frequencies, white noise feels bright and, at volume, harsh.

Pink noise drops by 3 decibels per octave, so each octave carries the same energy. It sounds like steady rain or a waterfall heard from a distance. Most natural "washes" of sound are close to pink.

Brown noise drops by 6 decibels per octave. It is named after Brownian motion, not the colour. It sounds like a low rumble: a plane cabin, a river heard through a wall, wind in a chimney. Almost all its energy sits below the range of human speech.

What the research does and does not show

The most cited study is Söderlund, Sikström and Smart (2007), who played white noise to children with and without ADHD during a memory task. The children with ADHD performed better with noise; the children without ADHD performed worse. The proposed mechanism is stochastic resonance: a nervous system running at low arousal benefits from a little extra input, while one already at the right level is disrupted by it. Follow-up work by the same group and others has been mixed, with some replications and some null results, and nearly all of it uses white noise and children.

For brown noise specifically there are no controlled trials worth citing. The 2022 wave of interest came from social media, not from a lab. That does not mean it does nothing. It means the mechanism that is well established is a different one: masking.

The "irrelevant speech effect" has been replicated for fifty years: hearing other people talk, even in a language you do not understand, measurably reduces performance on tasks that use working memory. Steady, broadband sound covers speech. That is the reliable benefit, and it applies whether you have ADHD or not.

So which one?

Pick by what you are trying to cover, then by ear.

• Open office or café: brown or pink. Speech sits between roughly 100 and 3,000 hertz, and a rumble with plenty of low-frequency energy covers it at a lower overall volume than white noise does.
• A loud flat, traffic, a neighbour's television: pink or a natural recording such as rain. Their spectrum overlaps most household noise.
• Tinnitus or a very quiet room where any hiss is irritating: brown. It is the least fatiguing to leave on for an hour.
• Sensitive to low rumble, or on laptop speakers: pink, or rain. Brown noise on small speakers turns into mud.

Volume matters more than colour. Set it just above the level of the sound you are masking and no higher. If you can feel the noise, it is too loud. If you notice you have stopped hearing it after a minute, it is right.

Noise is half of it

Noise stops the room from interrupting you. It does nothing about the other interruption, which is you. The pairing that works for most people is a masking sound plus a fixed block of time with a defined end, so that "I will just check" has a cost you can see. Twenty-five minutes is the usual length, not because it is magic but because it is long enough to get somewhere and short enough to start without dread.

The player above runs exactly that: brown noise or rain, a timer that counts down in the tab title, and a chime at the end. It runs in the browser on a laptop only, so the phone can go in another room, which is the subject of the next article.