White noise is a random sound with equal power at every frequency across its range: a flat spectrum. To the ear it's a bright, even hiss, like an untuned radio. For sleep, its job is masking: it raises the background level, so a door, a car or a neighbor stands out less. Small studies in noisy settings found it helped, but a 2021 systematic review rated the overall evidence that continuous noise improves sleep as very low quality. It's worth a try if noise wakes you, at a low volume and with a timer.
This page goes deeper on white noise alone. For how white, pink and brown noise differ and how they sound side by side, see our guide to white, pink and brown noise.
White noise, physically
Flat means every frequency band of the same width carries the same power. The Sound On Sound glossary defines white noise as "a random signal with a flat (constant) power spectrum density, ie. equal power within any frequency band of fixed width." So the band from 100 to 200 Hz carries as much power as the band from 10,000 to 10,100 Hz. Because our ears hear in octaves, which get wider as the pitch rises, white noise sounds bright and hissy. The comparison guide explains that effect.
Three facts that most white noise pages leave out:
- White is about the spectrum, not the shape of the signal. An engineering textbook chapter on noise (Woolf, Engineering LibreTexts) points out that "white noise is not always Gaussian noise." White only says how the power is spread across frequencies. The individual values can follow a bell curve, or be drawn evenly from a range, and still be white.
- Each moment is independent of the last. The same source describes white noise as independent of time: nothing in one instant predicts the next. That's what makes it sound so evenly random, with no rhythm to follow.
- Perfect white noise can't exist. Flat across all frequencies would need infinite energy, so real white noise is flat only across a limited range. In a sound file or app, that range ends at half the sample rate.
How white noise masks sounds
What wakes you is often not how loud a sound is, but how much louder it is than the background. A small 2005 sleep lab study tested this with white noise. Four healthy adults slept under three conditions: a normal night, recorded intensive care unit (ICU) noise, and ICU noise plus white noise (a fifth person completed the first two). With ICU noise alone, arousals from sleep rose from 13.3 to 48.4 per hour. With white noise added, they were 15.7 per hour, close to the normal night. Whether a sound caused an arousal depended on the jump from the background to the peak, which was about 17.5 to 17.7 dB in both noise conditions, not on the peak level itself.
That's the mechanism behind "white noise for sleep": it doesn't make the noise go away, it lifts the floor so the peaks jump less. It also explains why white noise does little in a room that's already quiet: there are no peaks to hide.
What studies on white noise and sleep found
The research on white noise specifically is small and uneven. Here's what we found and checked:
| Study | Who | What they did | What they found | Limits |
|---|---|---|---|---|
| Stanchina et al., 2005 | 4 healthy adults (5 for part) | Sleep lab, recorded ICU noise with and without white noise | White noise kept arousals near normal levels despite the ICU noise | Tiny group, recorded noise, one lab |
| Ebben et al., 2021 | 10 adults in New York City with sleep problems from noise at home | One week without, one week with a white noise machine, one week without | Less time awake after falling asleep (measured with a wrist device) and faster falling asleep (by sleep diary) | Only 10 people, no separate comparison group, a commercial white noise machine rather than an app |
| Mousavi et al., 2026 | 60 adults aged 65 and older in Iran | Both groups got sleep hygiene advice; one group also used white noise for 30 nights | Sleep quality score (PSQI) improved from 11.5 to 9.2 in the white noise group, with no significant change in the other group | Self-rated sleep only; the abstract gives no details on blinding |
| Ding et al., 2025 (meta-analysis) | 12 randomized trials, 1,301 participants | Pooled trials of white noise and sleep | Lower (better) PSQI scores in adults and older adults, in and outside intensive care units | Many hospital patients; the authors name heterogeneity and methodological quality as limits |
| Riedy et al., 2021 (systematic review) | 38 studies of continuous white or broadband noise | Rated the quality of the evidence with GRADE | Results ranged from better to worse sleep; overall evidence "very low" | Studies differed widely in noise, measures and settings |
What this adds up to: the best signals come from people with something to mask, like hospital noise or a loud street. The meta-analysis includes many patients in hospital, whose nights are unlike yours at home. And the systematic review, which looked at the widest set of studies, is the most cautious. The comparison guide also covers two 2026 sleep lab studies on pink noise that are relevant here, including one in which earplugs protected sleep better than noise did.
What the app's white noise sounds like
AI Meditation: Sleep & Calm describes its white noise as "a full, even hiss across all frequencies. Masks sudden sounds to help you focus or settle." It is generated live on your phone rather than played from a recording, so there's no loop point you might notice at 2am.
For the technically curious: the app draws every sample at random from an even range and plays it as a mono stream at 44,100 samples per second (from the app's code). By the rule above, its spectrum is flat up to 22,050 Hz, half the sample rate. That's our calculation, not a measurement of the sound coming out of your speaker, which also shapes what you hear.
You can set a timer from 5 to 90 minutes, after which the sound fades out and stops, or let it run until you stop it.
White noise for sleep: how to use it
- Use it when there's something to cover. Traffic, a snoring partner, a noisy building. In a quiet room, try without first.
- Start quiet. Turn it up only until the disturbing sound fades into the background, not until the hiss feels full.
- Play it from a speaker, away from your head, not from earbuds on the pillow.
- Set a timer instead of running it all night, unless the noise you're masking goes on all night.
- Try earplugs too. The AASM's sleep handout suggests "a white noise machine or earplugs" for a noisy room, and in a 2026 lab study earplugs beat pink noise at protecting sleep from traffic and aircraft noise.
- If the hiss feels sharp, try pink noise or brown noise. Both have less energy in the high frequencies.
How loud is safe?
There's no official volume guideline for sleep sounds, so the rule is: as quiet as still works. For hearing, the US National Institute on Deafness and Other Communication Disorders (NIDCD) says sounds at or below 70 dBA "even after long exposure, are unlikely to cause hearing loss," while long or repeated exposure at or above 85 dBA can cause it. The WHO suggests keeping your device's volume at no more than 60% of maximum and puts a whisper at around 30 dB and normal conversation at around 60 dB. The sleep lab studies in our comparison guide used about 40 to 50 dB, for example 46 dB in a 2017 study of broadband sound and falling asleep, so a sleep sound can sit well below normal conversation.
White noise for studying and the office
The same masking idea applies during the day: a steady hiss can cover conversations in an open office. The one controlled study we checked, from 2022 with 39 graduate students, found that white noise at 45 dB went with better attention and lower stress than normal office sound, while 65 dB helped working memory but raised stress. Our comparison guide describes it in full. Keep it low, and notice whether it helps you or just fills the silence.
White noise and sleep in the app
AI Meditation: Sleep & Calm has white noise alongside pink, brown, blue, violet and grey noise and four soft tonal sounds: Deep tone, Warmth, Crystal and Resonance. There's no rain, ocean or fan sound in the app. If you'd rather fall asleep to a voice, there are guided sleep meditations and sleep stories, read by AI voices. For a calmer evening overall, our sleep hygiene checklist covers the basics. See how the app works, try it for free, no account needed.
Your health
This app is a wellness app and does not replace medical advice. If sleep problems last for weeks or affect your day, talk to a doctor. If you notice changes in your hearing, see a doctor as well. The NHS insomnia page explains when to see a GP about sleep.
Sources
All pages accessed on September 25, 2026.
- Sound On Sound: White Noise (glossary). Flat power spectrum, equal power per band of fixed width.
- Woolf P. et al.: Noise Modeling: White, Pink, and Brown Noise, Pops and Crackles, in Chemical Process Dynamics and Controls, Engineering LibreTexts (CC BY 3.0). White light analogy, infinite energy, independent of time, white is not always Gaussian.
- Stanchina ML et al.: The influence of white noise on sleep in subjects exposed to ICU noise. Sleep Medicine 2005;6(5):423-428.
- Ebben MR, Yan P, Krieger AC: The effects of white noise on sleep and duration in individuals living in a high noise environment in New York City. Sleep Medicine 2021;83:256-259.
- Mousavi SAV, Salehian M, Mazlom SR: The effect of white noise on sleep quality and fatigue in community-dwelling older adults: a randomized controlled trial. BMC Geriatrics 2026;26(1):883.
- Ding Y et al.: Impact of white noise on sleep quality across age groups and in critically ill/non-critically ill patients: A systematic review and meta-analysis of randomized controlled trials. Sleep Medicine 2025;136:106869.
- Riedy SM, Smith MG, Rocha S, Basner M: Noise as a sleep aid: A systematic review. Sleep Medicine Reviews 2021;55:101385.
- Messineo L et al.: Broadband Sound Administration Improves Sleep Onset Latency in Healthy Subjects in a Model of Transient Insomnia. Frontiers in Neurology 2017;8:718.
- Basner M et al.: Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep. Sleep 2026;49(5):zsag001.
- Awada M et al.: Cognitive performance, creativity and stress levels of neurotypical young adults under different white noise levels. Scientific Reports 2022;12:14566.
- AASM: How to sleep better (PDF handout, 2012). White noise machine or earplugs.
- NIDCD: Noise-Induced Hearing Loss (last updated April 16, 2025). 70 and 85 dBA.
- WHO: Deafness and hearing loss: Safe listening (questions and answers, March 6, 2026). 60% volume, whisper and conversation levels.
