White Noise, Pink Noise, and Sleep: What the Newer Trials Actually Show

Bottom line: White and pink noise are not interchangeable magic frequencies. White noise has a plausible role as an acoustic masker when unpredictable environmental sounds are the actual problem, and a 2025 meta-analysis reported better sleep-quality scores in adult patient groups.[1] But the literature is heterogeneous, and a newer polysomnography experiment found that pink noise itself can reduce REM sleep.[4] The most defensible position is context-dependent benefit, not universal sleep enhancement.

What white noise is supposed to do

White noise spreads acoustic energy broadly across frequencies. In a bedroom, its most practical purpose is masking: a steady sound can make intermittent traffic, voices, doors, alarms or hospital noise less salient.

That is different from claiming that white noise directly deepens sleep or changes brain physiology in a beneficial way.

If masking is the mechanism, the benefit should be largest when the environment contains disruptive sound. A quiet bedroom may have much less to gain.

The 2025 meta-analysis is encouraging—but not clean

A 2025 systematic review and meta-analysis included 12 randomized controlled trials and 1,301 participants across infants, adults and older adults.[1]

In adults and older adults, pooled analyses found lower Pittsburgh Sleep Quality Index scores after white-noise interventions. The direction of effect was also favorable in both ICU and non-ICU settings.

That is meaningful evidence that white noise can improve perceived sleep quality in some populations.

But the review also reported substantial heterogeneity, especially for adult PSQI outcomes. The included studies varied in population, clinical setting, duration, sound delivery and outcome measurement.

So the pooled result should not become a universal claim that a sound machine improves everyone's sleep by a predictable amount.

Earlier evidence was much more mixed

A 2022 systematic review examined 34 studies involving 1,103 participants across white noise, pink noise and mixed auditory stimulation.[2]

Only 6 of 18 white-noise studies reported positive sleep findings. Pink-noise studies were more often positive, but both white- and pink-noise groups had relatively high risk-of-bias scores.

The authors concluded that strong evidence for auditory stimulation was lacking.

That older review and the newer 2025 meta-analysis are not necessarily contradictory. The newer analysis focused on randomized trials and pooled selected outcomes, while the older review emphasized the broader methodological weakness and inconsistency of the literature.

Hospitals may be a better use case than quiet bedrooms

Hospital sleep is frequently disrupted by alarms, staff activity, equipment and roommate noise.

A 2025 systematic review of sound machines in hospitalized adults found evidence suggesting improved sleep efficiency, but studies were too heterogeneous for a clean meta-analysis.[3]

This makes mechanistic sense: when unpredictable environmental noise is the bottleneck, masking it may help.

That does not prove that the same intervention improves sleep in a quiet home environment.

Pink noise is not automatically “better”

Pink noise contains relatively more energy at lower frequencies than white noise and is often described as softer or more natural.

Older studies have generated interest in pink-noise stimulation and slow-wave activity. This has led to consumer claims that pink noise boosts deep sleep, memory or recovery.

But newer evidence is a useful reality check.

A 2026 laboratory study exposed healthy adults to intermittent environmental noise, continuous pink noise, earplugs and combinations while measuring sleep with polysomnography.[4]

Environmental noise reduced N3 deep sleep. Pink noise modestly reduced some noise-related fragmentation—but pink noise itself reduced REM sleep compared with a quiet control condition.

That means a masking sound can simultaneously solve one problem and create another.

“More deep sleep” is not the same as “better sleep”

Sleep architecture is a system, not a scoreboard where maximizing one stage is always beneficial.

A sound intervention might alter arousals, N3, REM, awakenings or perceived sleep quality differently.

So claims such as “pink noise increases deep sleep” need to preserve the rest of the architecture. If REM falls or sleep becomes fragmented, a single favorable stage metric does not tell the whole story.

Volume matters

A sound that masks environmental noise must be audible, but louder is not automatically better.

Excessive nighttime sound can itself become an environmental stressor and may interfere with sleep. The optimal level likely depends on the competing noise, distance from the speaker, room acoustics and individual sensitivity.

Research protocols use controlled sound levels. Consumer devices used at arbitrary volume are not automatically equivalent.

Individual noise sensitivity probably matters

People differ dramatically in how they respond to sound.

Someone who wakes to every hallway noise may benefit from masking. Someone who finds steady noise irritating may sleep worse.

The 2022 review specifically highlighted noise sensitivity and individual differences as variables future studies need to account for.[2]

That is another reason a population-average result should not become a one-size-fits-all recommendation.

White noise versus earplugs

If the problem is external sound, reducing incoming noise and masking it are two different strategies.

The newer pink-noise experiment found that earplugs were also useful under environmental-noise exposure.[4]

This matters because the most evidence-based question may not be “which color of noise is best?” but rather:

What is the least disruptive way to reduce the specific noise that is waking this person?

Sometimes that may be a sound machine. Sometimes it may be earplugs, room changes, building changes or removing the source.

Bottom line

White noise has a credible evidence signal, especially in noisy clinical environments and in newer randomized-trial synthesis.[1,3]

But the broader literature remains heterogeneous, and older systematic evidence did not find strong support across studies.[2]

Pink noise is even more nuanced: a recent polysomnography study showed that it can reduce REM sleep despite partially masking environmental disruption.[4]

The most defensible verdict is useful environmental masking for some sleepers, with no basis for promising universally deeper or more restorative sleep.

Related reading

• Sleep Temperature and Cooling
• How Accurate Are Sleep Trackers?
• Subjective vs Objective Sleep
• Why Sleep Studies Disagree