A sound machine promises a simpler night: turn it on, drown out the traffic and sleep. But there is a catch. A steady sound may hide the noises that wake you, while also changing sleep itself. In a controlled 2026 experiment, continuous pink noise reduced REM sleep compared with a quiet night. In other experiments, broadband sound helped blunt the impact of intermittent noise.
Both results can be true. The key is to distinguish masking an external disturbance from improving sleep in the absence of that disturbance. White and pink noise are not interchangeable treatments, and neither is proven to make an already quiet bedroom more restorative. Here is what the experiments actually measured, where they disagree and how to make a sensible choice.
What are white and pink noise, exactly?
White noise has roughly equal power per hertz of frequency, giving it a flat spectrum and a bright, steady hiss. Pink noise follows approximately 1/f: at twice the frequency, its power per hertz is halved. It therefore places relatively more emphasis on low frequencies and tends to sound deeper. The infographic below shows the difference and familiar sounds that resemble each colour.
Neither is inherently better for sleep. To compare how they sound, try these white-noise and pink-noise examples at low volume. They are third-party recordings, not loudness-matched tests.
The real benefit may be the sound you no longer notice
Picture a silent bedroom and a car door slamming outside. Now imagine the same sound over the steady rush of a fan. The door has not become quieter, but the jump from background to peak is smaller. That is acoustic masking: one sound makes another harder to detect. It is not the same as stopping sound from entering the room, which is what insulation or well-fitted earplugs attempt to do.
Why do these two kinds of noise sound different? Their frequency spectra provide the answer.
What changes is the balance of low and high frequencies. That is why two steady sounds can feel so different.
No colour is a proven shortcut to better sleep.
Relative power per Hz on logarithmic axes; curves meet at 1 kHz.
Why: equal power per hertz produces a brighter hiss.
Why: relatively more low-frequency energy. Each octave contains approximately equal total power.
In nature? Rain, wind and surf are rough analogies, not exact spectral matches.
And music? Many recordings favour lower frequencies, but their notes and rhythms are not random noise.
The distinction matters because more masking is not automatically better. Raising a machine’s volume can make sudden traffic less noticeable, but it also exposes the sleeper to more continuous sound. And a masker may obscure sounds you need to hear, including an alarm or a child crying.
Three experiments, one uncomfortable question
Does steady noise protect sleep, disturb it, or do both? The answer depends on what it replaces. A comparison with a noisy hospital corridor asks a different question from a comparison with silence.
1. A striking rescue in a simulated intensive care unit
In a 2005 laboratory experiment, four healthy volunteers completed all three conditions: a baseline night, recorded intensive-care-unit noise and the same ICU noise with added mixed-frequency white noise. The EEG arousal index, which counts brief changes in brain activity during sleep, rose from 13.3 to 48.4 per hour under ICU noise, then fell to 15.7 with added white noise. An EEG arousal is not necessarily a full awakening. A fifth participant completed only two conditions.
The result is impressive, and extremely small. It shows that masking can matter when background-to-peak contrast is large; it does not test whether white noise is preferable to quiet. It also does not establish improved next-day health or long-term benefit.
2. In a quiet room, pink noise reduced REM sleep
A much more informative comparison came from Basner and colleagues in 2026. Twenty-five healthy adults spent seven nights in a laboratory under varying conditions: quiet, intermittent environmental events, continuous pink noise at 40 or 50 dBA, and foam earplugs. Here, dBA means A-weighted decibels, a sound-level measure adjusted approximately for human hearing sensitivity; it is not a prescribed sleep-volume setting. The researchers monitored sleep stages with polysomnography, not just questionnaires.
Against the quiet control, 50 dBA pink noise alone reduced average REM sleep from 118.1 to 99.5 minutes, an 18.6-minute difference (about 16%; p < 0.001 in the study’s REM analysis). REM is the sleep phase marked by rapid eye movements and vivid dreaming. Intermittent environmental noise, by contrast, mainly reduced N3, the deepest stage of non-REM sleep. Adding pink noise to the environmental noise slightly reduced some fragmentation but generally worsened sleep structure relative to quiet. Earplugs protected sleep more effectively than pink noise, although they too had limits at the loudest exposure.
Mean REM duration: quiet control versus continuous 50 dBA pink noise, n = 25. The experiment lasted seven nights. This is a short-term result, not evidence of permanent injury or established health harm.
Participants’ subjective ratings of sleep, alertness and mood were also significantly worse after environmental-noise and pink-noise exposure in the study’s overall analysis. No clear morning cognitive, hearing or cardiovascular test differences emerged. That absence of short-term differences does not establish long-term safety.
3. Another pink-noise experiment found a protective effect
In a separate 2026 crossover pilot, 12 healthy adults slept under quiet, traffic, continuous pink-noise and combined conditions. Traffic events produced brief physiological sleep disturbances and changes in several blood metabolites; the pink-noise masker attenuated some of these effects. Yet participants did not report better sleep or restoration with pink noise, and some perceived measures were worse than quiet.
That is not a contradiction to erase. A sound can reduce the disturbance caused by another sound without being beneficial when played on its own. The metabolite results are exploratory markers, not proof of disease prevention.
But a meta-analysis also found benefits of white noise
A 2025 systematic review and meta-analysis pooled 12 randomised trials of white noise in different populations. It found improvements in reported sleep quality in some adult patient groups: among adult participants, the pooled difference on the Pittsburgh Sleep Quality Index (PSQI), a questionnaire scored from 0 (best) to 21 (worst), was −3.70 points (95% CI −4.90 to −2.50). That means better reported sleep, not necessarily more objectively measured deep or REM sleep. ICU and non-ICU clinical subgroups also showed improvements.
Why does this not settle the question? The trials involved different patients, environments, interventions and outcomes. The authors reported substantial heterogeneity. A clinical patient’s questionnaire score is not the same outcome as a healthy sleeper’s REM minutes, and white noise is not identical to continuous pink noise. The results support possible context-specific benefits, not a universal prescription.
Is pink noise better than white noise?
There is no convincing head-to-head evidence that one colour is the better sleep aid. A 2022 systematic review examined 34 auditory-stimulation studies involving 1,103 people. Findings varied widely across sleep settings, sound levels, equipment and outcome measures. Several studies reported positive results, but the evidence was too heterogeneous to give a reliable overall winner.
Only one of those studies directly contrasted conditions labelled white and pink noise. Their sound sources and levels were not matched closely enough to isolate colour as the cause of different outcomes. More bass or a pleasanter sound to an individual listener is a reasonable preference; it is not a demonstrated biological advantage.
The pink-noise study that is often misquoted
Some headlines about pink noise and deep sleep refer to something technically different: closed-loop acoustic stimulation. In a small experiment involving 13 older adults, brief pink-noise pulses were timed to a particular phase of slow brain oscillations. The researchers observed increases in slow-wave activity during the stimulation intervals and better performance on one overnight memory measure.
A speaker playing a constant hiss all night cannot reproduce that protocol. Even the laboratory result did not mean an across-the-board increase in slow-wave activity throughout the entire night. Precisely timed brain stimulation is not evidence for leaving continuous pink noise on while you sleep.
White noise vs pink noise: what the comparison actually tells us
| Question | White noise | Pink noise |
|---|---|---|
| How is the acoustic energy distributed? | Approximately equal power per hertz; brighter hiss | Approximately equal power per octave; deeper sound |
| Can it mask sudden sounds? | Sometimes, under noisy conditions | Sometimes, under noisy conditions |
| Proven superior in a quiet bedroom? | No | No |
| Evidence of sleep benefit in some clinical groups? | Yes, but heterogeneous and often subjective | Mixed; depends on protocol and setting |
| Concern raised by controlled study? | Possible unnecessary sound exposure; long-term effects uncertain | Reduced REM sleep at 50 dBA in one short-term healthy-adult trial |
| Is one colour reliably better? | No adequately controlled comparison establishes that. | |
A practical decision: quiet, earplugs or background sound?
If your bedroom is quiet: there is no compelling reason to add continuous sound solely to improve sleep architecture. Start with the simpler option: quiet, if you find it comfortable.
If traffic, voices or doors interrupt your sleep: consider reducing the noise at its source, improving the window or door seal, or using comfortable, properly fitted earplugs where appropriate. Unlike masking, these options aim to lower the sound reaching the ear. Earplugs outperformed pink noise in the 2026 laboratory comparison, though no intervention blocked every noise event.
If those measures are impractical: a steady fan or low-level white or pink noise may make sudden sounds less intrusive. Choose the sound you tolerate and the lowest setting that does the job, rather than chasing a supposedly therapeutic frequency. Keep emergency alarms and important household signals audible. Be cautious if you need to hear an infant, a dependent adult or other safety-critical sounds.
If you use it every night: there is little controlled evidence on long-term effects, habituation or whether people eventually struggle without a familiar sleep cue. A bedtime association is plausible; physiological dependence is not demonstrated. Monitor whether the sound is solving an actual problem rather than becoming an unnecessary default.
Sound level, hearing and infants
Noise exposure depends on level, distance and duration. The widely cited NIOSH 85 dBA for eight hours figure is an occupational hearing-risk benchmark, not an overnight target and not a guarantee that a bedroom sound level is harmless to sleep. Headphones or earbuds worn overnight add practical considerations such as fit and pressure; they are not necessary to obtain a masking effect from a room sound source.
For infants the margin for error matters more. A 2014 test of 14 infant sound machines found that at their maximum volume and at 30 cm, all exceeded 50 dBA and three exceeded 85 dBA. These are measurements of device output under a specific test condition, not evidence that all use causes injury. Still, they are a strong reason to place a device well away from a child’s head, keep volume low, avoid maximum settings and question the need for continuous exposure.
What to take away
A sound can make a disruptive environment more tolerable without improving sleep in a quiet room. If you already sleep well in silence, there is no evidence-based reason to add a soundtrack. If outside noises wake you, reduce them where possible; otherwise try a low-level sound that masks the interruptions without becoming an additional disturbance. The colour is a matter of acoustics and preference, not an established hierarchy of sleep benefits.
Frequently asked questions
Is pink noise better than white noise for sleep?
Not on present evidence. The best choice depends on what sound you are trying to mask, personal comfort and volume. Direct, well-matched comparative trials are missing.
Does pink noise improve deep sleep?
Some laboratory studies used precisely timed pink-noise pulses to alter brain oscillations. They cannot be used to claim that continuous pink noise improves deep sleep. One 2026 trial instead found a reduction in REM sleep during continuous 50 dBA pink-noise exposure.
Does white noise help with traffic noise?
It can make intermittent noise less noticeable in some environments. Yet reducing noise at the source or using appropriate ear protection may protect sleep more effectively than masking it.
Is it safe to use a sound machine every night?
Long-term sleep effects remain poorly studied. Avoid unnecessary high volume and place devices well away from the ear, especially for infants. Occupational hearing thresholds are not overnight bedroom recommendations.
Sources and evidence notes
Basner et al. (2026). Seven-night polysomnography study, n = 25. Pink noise, environmental noise and earplugs; see Tables 2–3 for objective sleep-stage outcomes.
Stanchina et al. (2005). Controlled ICU-noise simulation, four participants completing all three conditions (five in partial conditions). Arousal indices reported in the abstract.
Vincens et al. (2026). Exploratory crossover pilot, n = 12; sleep and metabolomics effects of traffic noise and pink-noise masking.
Ding et al. (2025). Systematic review and meta-analysis of 12 randomised controlled trials of white noise across several clinical and age groups; heterogeneous patient-reported effects.
Capezuti et al. (2022). Systematic review of 34 auditory-stimulation studies and 1,103 participants; substantial variation in design and outcomes.
Papalambros et al. (2017). Closed-loop pink-noise pulses in 13 older adults, distinct from continuous room sound.
NIOSH. Occupational noise-exposure benchmark, not a bedroom-volume recommendation.
Hugh et al. (2014). Sound-level measurements from 14 infant sleep machines.
Editorial method: priority was given to controlled human experiments, objectively measured sleep stages and systematic reviews. Differences between clinical questionnaire outcomes and healthy-adult laboratory physiology were not pooled into a single verdict. Visuals are original schematic or descriptive presentations of reported data, not independent experiments. Featured illustration: original Art Nouveau-inspired editorial artwork for Mike’s Balance.