Pink noise equal energy in every octave

What is pink noise?

Pink noise is random sound in which every octave carries the same power. Its power density is proportional to 1/f, so it falls by 3.01 dB each time the frequency doubles and by 10 dB for every tenfold rise. The band from 40 to 60 Hz holds as much power as the band from 4,000 to 6,000 Hz, a hundred times higher in pitch.

That balance matches the way we hear. The ear divides pitch into octaves, and pink noise fills each of them equally, so it sounds even from bottom to top: fuller and softer than the hiss of white noise, with less rumble than brown noise. People most often compare it to steady rain or wind in trees.

Pink noise is also called 1/f noise, after its formula. The name pink comes from a loose analogy with light: white light has all colours equally, and light tilted towards the long, low-frequency red end looks pink. Pink noise is tilted the same way, but only halfway to red noise, which is another name for brown.

Pink noise vs white noise vs brown noise

Pink noise is flat per octave, white noise rises by about 3 dB per octave compared with it, and brown noise falls by about 3 dB. The table shows what that means across the range, with the octave around 1,000 Hz as the zero point.

Every 3 dB is a doubling or halving of power, so over those eight octaves white noise puts about 250 times more power into its top octave than its bottom one, while brown does the reverse. Pink sits in the middle, which is why it is the easiest to listen to for people who find white too sharp and brown too muffled.

Pink vs brown noise, in practice: brown has more rumble and less detail, pink has more air and sounds closer to rain. If the sounds that disturb you are low (traffic, a lift, bass through the wall), brown covers them with less volume; if they are in the middle and upper range, pink does. The brown noise page covers brown in depth, and all seven colours are compared on the page about the colors of noise.

Why sound engineers use pink noise

Pink noise is the standard reference signal in audio engineering because it puts equal power into every octave. When a sound engineer plays pink noise through a speaker and looks at it on an analyser that shows octave or third-octave bands, a perfect system shows a flat line. Any bump or dip reveals a problem with the speaker or the room.

White noise would look like a rising slope on the same display and would push most of its power into the treble. Pink noise tests the whole range more evenly.

This history is part of why pink noise sounds natural to many listeners: it was chosen precisely because its energy is spread the way hearing is organised.

Does pink noise improve deep sleep and memory?

Pink noise improved memory only in a special laboratory method: very short bursts of pink noise timed by a computer to the brain's slow waves during deep sleep. A pink-noise track playing all night was not what these studies tested.

The method was introduced by Ngo, Martinetz, Born and Mölle (Neuron, 2013). Sleepers wore EEG electrodes, and whenever a slow oscillation (a brain wave slower than 1 Hz) reached its up state, the system played two quiet pink-noise clicks of 50 milliseconds. The clicks strengthened the slow waves and the sleep spindles, and people remembered more word pairs the next morning. When the same clicks were played out of phase with the waves, nothing happened. Timing is the whole effect.

Later studies extended it to older people:

Why a phone cannot copy this: the clicks have to land on a wave that lasts about a second, at a moment that only an EEG can detect. A continuous sound hits every phase of every wave equally, which is closer to the out-of-phase condition that did nothing. So the honest summary is that pink noise helped memory in the lab only when very short clicks were timed to deep-sleep waves.

Is pink noise good for sleep?

Steady pink noise has two sleep studies that point in opposite directions, and the more careful one found a cost. The first, from China (Zhou and colleagues, 2012, Journal of Theoretical Biology), tested 40 people overnight and 10 in naps, each with one pink-noise session and one quiet session. The share of what the authors called stable sleep rose with pink noise. Stable sleep was estimated from the heartbeat (cardiopulmonary coupling), not from full sleep recording, and the result has not been replicated with polysomnography.

The second is the most careful recent lab study of noise and sleep (Basner and colleagues, Sleep, 2026). Twenty-five healthy adults each spent seven nights in a sleep laboratory with full polysomnography. Traffic-type noise events of 45–65 dBA reduced deep (N3) sleep. Pink noise at 40 or 50 dBA on its own reduced REM sleep. Adding pink noise to the traffic events made sleep structure worse overall, despite small improvements in fragmentation. Earplugs prevented nearly all the effects of the traffic noise until they began to fail at 65 dBA. After nights with pink noise, people rated their sleep, alertness and mood worse.

The authors caution against widespread and indiscriminate use of broadband noise and call for research on colour, level and long-term use. Two studies cannot settle the question, but together they justify a careful approach: pink noise may help you fall asleep by covering sounds, and it is not a sound to leave running all night on the belief that it deepens sleep.

How to use pink noise for sleep

Use pink noise to fall asleep, keep it quiet, and let a timer end it unless noise wakes you during the night. That approach takes both the masking evidence and the REM finding seriously.

• Set the timer to 30 or 60 minutes if you need help only with falling asleep; the sound fades out over the last minute.
• Keep the level low. Basner's participants heard pink noise at 40 and 50 dBA; a bedroom sound should cover disturbing peaks and no more. The WHO recommends continuous bedroom noise below about 30 dB.
• Put the speaker away from your head, and use a speaker rather than earphones for anything longer than the first hour.
• If traffic is the problem, try earplugs first. In the 2026 lab study they worked better than pink noise.
• If you use pink noise all night because the night itself is noisy, try a few nights with and a few without, and note how rested you feel in the morning.

The mixer on this page has seven noise colours and seven nature sounds with a volume for each, ready mixes and a timer from 15 minutes to 8 hours. Pink noise with a little rain or stream gives a softer, more natural bed than pink noise alone.

Pink noise for focus, studying and ADHD

Pink noise is one of the two noise colours with research on attention, and the result depends on whether you have ADHD. A 2024 meta-analysis (Nigg and colleagues) pooled studies of white and pink noise and found a small benefit on lab attention tasks for children and young adults with ADHD or ADHD symptoms, and a small harm for people without ADHD. The details and numbers are on the white noise page.

Pink noise is often chosen over white for work because it is less sharp over long periods. The generator's focus mix uses pink noise with a soft stream on top. Try it for a working session, compare it with a quiet session, and keep it only if it helps you finish more.

Pink noise myths: what it does not do

Pink noise is useful for masking and pleasant to many listeners, but several popular claims go beyond the research.

• Claim: pink noise played all night boosts deep sleep and memory. The memory studies used 50 ms clicks timed to brain waves; steady pink noise shortened REM sleep in the most careful recent study.
• Claim: pink noise is proven to improve sleep. A systematic review of steady noise and sleep (Riedy and colleagues, 2021) rated the evidence very low quality.
• Claim: pink noise treats ADHD. The meta-analysis found a small effect on lab attention tasks, not a treatment effect, and a small harm in people without ADHD.
• Claim: a pink-noise app can do what the lab did. The lab needed EEG and precise timing; a continuous track cannot follow your brain waves.

None of this makes pink noise bad. It means the reasons to use it are the ordinary ones: it covers background sound and many people like how it sounds.