White Noise

A flat, bright hiss — the most studied noise colour, the most useful for covering voices, and the easiest one to use badly.

What White Noise Actually Sounds Like

White noise is the sound of an FM radio tuned between stations, an old television showing static, air escaping from a valve, or a hairdryer heard from the next room. It is bright, even and slightly abrasive, and it sits forward — it sounds like it is coming from a specific place rather than filling the room the way brown noise does.

The single most surprising thing about white noise is where its energy actually is. Equal power in every hertz sounds like an even distribution, but frequency bands get exponentially wider as you go up: the octave from 10 kHz to 20 kHz contains as many hertz as everything below 10 kHz put together. So half of white noise's total power lives in the top octave alone — a region most people cannot hear much detail in, but can absolutely feel as hiss. That is why white noise is described as sharp, and it is the reason every other colour on this site exists.

The player above generates the signal live rather than looping a file, so there is no repeat point and no seam. Both channels are drawn from independent random sequences, which is why it sounds wide on headphones rather than pinned to the centre of your head.

The Spectrum, Measured

White noise is defined by having a flat power spectral density: the same power in every hertz, from the bottom of the audible range to the top. The slope, expressed the way the other colours are, is 0 dB per octave.

Measured over 120 seconds of this player's output at 48 kHz, using Welch's method and a least-squares fit from 100 Hz to 10 kHz, the slope came out at 0.00 dB per octave with an uncertainty of ±0.08 dB. That is as flat as a generated signal realistically gets, and it is the reference against which the other four colours on this site were measured — pink at −3.07, brown at −5.98, blue at +3.08.

White noise is also the raw material for all of them. Every other colour here starts as white noise and is shaped by a filter chain; brown is what you get by integrating it, pink by tilting it 3 dB per octave downward, blue by tilting it the same amount upward.

One consequence of that flat spectrum is that white noise has, by a wide margin, the most energy in the 2–5 kHz band where human hearing is most sensitive. This is why it needs to be normalised for perceived loudness rather than raw signal level. Every colour on this site is set to −20 LUFS by ITU-R BS.1770-4 K-weighting, within a 0.6 dB spread, so moving between them does not produce a jump.

What White Noise Is Genuinely Good At

Covering speech. This is the thing white noise does better than any other colour, and the reason it is the standard choice in open-plan offices, clinics and consulting rooms. Speech intelligibility is carried mostly by consonants, which live in the 2–4 kHz region; vowels carry the volume but very little of the meaning. White noise has plenty of energy exactly where the consonants are, so it does not merely make a conversation quieter, it makes it unintelligible — which is the outcome that actually stops you listening in.

Sudden broadband events. A door slamming, a dog barking, a car horn, a floorboard. These are short and spectrally wide, and a flat masker covers all of them at once rather than half of each.

Tasks rather than nights. White noise is the colour with the strongest case for use during focused work, and the colour where that case actually has evidence behind it (see below). It also suits shorter sessions better than long ones, because the same high-frequency content that makes it effective is what makes it wearing after several hours.

Small speakers. Unlike brown noise, white noise reproduces almost fully on a phone, a laptop or a cheap Bluetooth speaker, because nothing important is happening in the bass. If the only device you have is the one in your pocket, white noise is the colour least degraded by it.

What White Noise Is Bad At — and One Real Safety Issue

Long overnight sessions. The top-octave energy that makes white noise so effective is also what makes it tiring. Listening fatigue from broadband noise is largely a treble phenomenon, and eight hours of it is a common reason people abandon white noise machines and go looking for something darker.

Low-frequency rumble. White noise has no more energy at 60 Hz than it does at 6 kHz, which is nowhere near enough to bury traffic, an HVAC unit or a neighbour's bass. For those, brown noise is the correct tool and white noise will not get you there at any volume you would tolerate.

The volume problem, which is genuinely worth taking seriously. In 2014, Hugh and colleagues measured 14 infant sleep machines at maximum volume and published the results in Pediatrics. Every device exceeded 50 A-weighted decibels at 30 cm, and three of them produced more than 85 dBA — a level which, sustained for more than eight hours, would exceed adult occupational noise exposure limits. That study is about hardware turned all the way up next to a cot, not about white noise as an idea, but the lesson generalises: the risk in noise machines is the level and the duration, not the colour. Put the source across the room rather than beside the pillow, and set it no louder than it needs to be to do its job.

People who find it unpleasant. A meaningful number of listeners describe white noise as a hiss inside their head, or as tinny and sharp. That is not a fault in the signal, it is a real perceptual response to a spectrum weighted toward the most sensitive part of human hearing. If that is you, pink noise is the natural next step and brown noise is the opposite extreme.

What the Research Actually Shows

White noise is the only colour here with a real evidence base, which makes it the one place on this site where the honest summary is genuinely mixed rather than simply absent.

For sleep, the evidence is weak. Riedy, Smith, Rocha and Basner, Noise as a sleep aid: A systematic review (Sleep Medicine Reviews, 2021; 55:101385) screened three databases and assessed risk of bias across 38 included articles. Their conclusion was that the evidence for continuous noise improving sleep is very low quality. This review is frequently cited on noise-app websites as though it endorsed white noise; it does not. It is worth reading the actual conclusion rather than the summaries of it.

For attention, the evidence is better and more specific. Nigg and colleagues (Journal of the American Academy of Child and Adolescent Psychiatry, 2024; 63(8):778–788) ran a systematic review and meta-analysis on white and pink noise and task performance in young people with ADHD or elevated attention problems. Their finding, stated precisely: white and pink noise provide a small benefit on laboratory attention tasks for individuals with ADHD or high ADHD symptoms, but not for non-ADHD individuals. Two things follow from that. It is a small effect on lab tasks, not a demonstrated improvement in schoolwork or daily function. And if you do not have ADHD, this particular result is not about you.

The proposed mechanism dates back to Söderlund, Sikström and Smart (Journal of Child Psychology and Psychiatry, 2007; 48:840–847), who reported that auditory white noise improved cognitive performance in children with ADHD while degrading it in controls, and framed it in terms of stochastic resonance — the idea that a moderate amount of noise can help a system detect a signal it would otherwise miss. It is a coherent hypothesis with a plausible mechanism, and it is still a hypothesis.

None of this is medical advice, and none of it constitutes a treatment. If sleep or attention problems are affecting your life, that is a conversation for a clinician.

Using It Well

Distance beats volume. Because white noise is bright and directional, moving the source further away changes the character of the sound as well as the level — the room absorbs high frequencies faster than low ones, so a speaker across the room delivers something noticeably softer than the same speaker at the same setting beside your bed. This is the cheapest available way to make white noise more tolerable.

Turn it down once the target disappears. Masking is a threshold effect. Once the conversation next door is no longer intelligible, additional volume adds exposure and buys nothing.

Try it for work before you try it for sleep. Given where the evidence actually points, a focused work session is the better first test. If it helps you concentrate but wears on you overnight, that is a completely normal outcome — most people who use noise regularly end up using a bright colour by day and a dark one at night.

How It Compares With the Other Colours

White noise is the flat reference point, and every other colour here is a deliberate departure from it. Pink noise takes 3 dB per octave off the top and is what most people mean when they say they want white noise but softer. Brown noise takes off twice as much and turns hiss into rumble. Green noise keeps the middle and discards both ends. Blue noise goes the other way entirely and is brighter still, which is a curiosity rather than a comfort.

For covering voices, white noise remains the best of the five. For everything else, one of the others is usually a better answer.

Frequently Asked Questions

Related pages

• Brown Noise for Sleep — The free web player, plus the full guide to brown noise for sleep, focus, and tinnitus.
• Pink Noise — Equal energy in every octave, measured at −3.07 dB per octave — the natural-sounding default and the audio industry's calibration signal.
• Brown Noise — The deepest colour, measured at −5.98 dB per octave — best for traffic rumble and long overnight sessions.
• Green Noise — The mid-frequency colour — a pink base with a broad 500 Hz emphasis, and the only one of the five with no standard definition.
• Blue Noise — The bright end of the spectrum at +3.08 dB per octave — an engineering signal that is genuinely useful against high-pitched noise, and a poor choice for sleep.
• Brown vs White Noise — The widest gap on the site — 5.98 dB per octave, about 38 dB apart by 8 kHz — and what each colour can and cannot cover as a result.
• White vs Pink Noise — Flat per hertz against flat per octave — two kinds of even, why the ear prefers the second, and why no trial has ever ranked the two.
• Brown Noise for ADHD — The 2024 meta-analysis with its real numbers — a small benefit on lab attention tasks in ADHD, a negative effect without it, and zero studies of brown noise.
• Brown Noise for Focus — Why concentration is a masking problem measured in speech intelligibility, and why brown noise beats every colour for rumble but loses to white for voices.
• Brown Noise App — Which brown noise app to install, whether it is really free, and the five things an installed app does that a browser tab is not allowed to.