Pink noise worsens sleep quality when used to block out traffic and city noise

Pink noise—often promoted as a sleep aid—may actually worsen sleep by reducing REM sleep, while simple foam earplugs offer far better protection against nighttime noise, according to a new study published in Sleep.

Environmental noise—such as traffic, aircraft, or alarms—is known to disturb sleep and contribute to long‑term health problems. Deep sleep is particularly vulnerable, and chronic disruption has been linked to cardiovascular disease, metabolic disorders, and impaired daytime functioning. At the same time, broadband noise like pink or white noise has been marketed as a way to mask unwanted sounds and promote rest. Despite their popularity, scientific evidence supporting broadband noise as a sleep enhancer has been surprisingly thin.

Led by Mathias Basner from the University of Pennsylvania, the researchers designed a tightly controlled seven‑night sleep‑lab experiment involving 25 healthy adults with an average age of 28.5 (seven males). Each participant slept under different conditions, including quiet nights, nights with intermittent environmental noise (e.g., sounds of cars and trains), nights with continuous pink noise alone, and nights combining environmental noise with either earplugs or continuous pink noise (at two different volumes).

Every night was monitored using full polysomnography—the gold standard for measuring sleep stages—while mornings included cognitive tests, cardiovascular measurements, hearing checks, and surveys.

Environmental noise alone significantly reduced deep sleep—on average a 23.4-minute decrease—replacing restorative deep sleep with lighter sleep stages. Interestingly, pink noise did not help, instead generating its own problem. Pink noise was found to be associated with an 18.6-minute average decrease in REM sleep—the sleep stage crucial for memory, emotional regulation, and brain development.

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When pink noise was added to environmental noise, sleep became even more disrupted. Participants experienced less deep sleep, less REM sleep, more time awake, and lower sleep efficiency overall. Evidently, pink noise not only failed to protect sleep from environmental noise, but it made sleep architecture worse.

Earplugs provided a very different outcome. The foam earplugs used in the study restored most of the deep sleep lost to environmental noise, recovering about 72% of the reduction in deep sleep. In nearly every sleep measure, nights with earplugs looked statistically indistinguishable from quiet control nights. Participants also reported feeling more rested and less fatigued compared to nights with environmental noise (whether masked by pink noise or not).

The authors concluded that the negative effects of pink noise on REM sleep caution against the widespread and indiscriminate use of broadband noise. They specifically advised discouraging its popular use in newborns and toddlers, noting that REM sleep is critical for neurodevelopment in these age groups, though further confirmatory studies are needed.

The study does have limitations. For example, it was only conducted over a short‑term period, involved only healthy young adults, and tested only two levels of pink noise. Real‑world environments are more complex, and long‑term effects remain unknown.

The study, “Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep,” was authored by Mathias Basner, Michael G. Smith, Makayla Cordoza, Matthew S. Kayser, Michele Carlin, Adrian J. Ecker, Yoni Gilad, Sierra Park‑Chavar, Ka’alana Rennie, Victoria Schneller, Sinead Walsh, Haochang Shou, Quy Cao, Magdy Younes, Daniel Aeschbach, and Christopher W. Jones.