Nighttime environmental noise is not just an annoyance but can disturb sleep and raise the risk of illness and premature death. The World Health Organization (WHO) recommends that traffic noise at night remain below 40 to 45 decibels (dB) to prevent harmful effects on sleep, yet recent analysis indicates that millions of people are permanently exposed to noise levels of at least 50 dB.
Interestingly, many people turn to other sounds to distract them from the unwanted noise pollution, using sleep apps or audio streaming services. But new research suggests that one popular solution, pink noise, may actually interfere with the brain’s recovery process overnight.
A study from the University of Pennsylvania Perelman School of Medicine, published in Sleep, found that pink noise may reduce restorative REM sleep. Earplugs, by contrast, were significantly more effective at protecting sleep against traffic noise, addressing the popularity of ambient sleep aids.
Read more: A Rare Hearing Disorder Can Make Sounds Loud and Uncomfortable
Promoting Healthy Sleep With Ambient Sound
Over the course of a healthy night, the body cycles through multiple sleep stages — light sleep, deep sleep, and rapid eye movement (REM) sleep — each serving a distinct restorative function. Deep sleep primarily supports physical recovery, while REM sleep is characterized by heightened brain activity associated with emotional regulation and dreaming. Moving through these phases several times each night helps us awake feeling refreshed.
However, increasing traffic noise often disrupts both falling and staying asleep, prompting people to seek acoustic buffers. Broadband sounds, often categorized by “noise colors” such as white, brown, or blue, vary in their energy distribution across audible frequencies.
Pink noise, characterized by balanced, lower-pitched sound similar to steady rainfall or even the auditory environment of the womb, has been suggested in prior research to promote sleep more effectively than white noise. But whether it truly protects sleep remained unclear.
Combining Pink Noise With Environmental Noise Had Worse Outcomes
Researchers monitored 25 healthy adults aged 21 to 41 during a seven-night stay in a sleep laboratory, exposing them to different sound conditions: environmental noise averaging 43.2 dB, pink noise up to 50 dB, combinations of the two, and environmental noise paired with earplugs. Electrodes tracked sleep stages while participants completed cognitive tests and surveys.
Environmental noise alone reduced deep sleep by an average of 23 minutes, though earplugs prevented deep sleep loss until noise levels reached roughly 65 dB.
Pink noise did not significantly cut deep sleep, but it was associated with nearly 19 fewer minutes of REM sleep, even though the sound volume was comparable to moderate rainfall. When pink noise and environmental sounds were combined, outcomes worsened: both deep and REM sleep shortened, and participants spent more time awake than during noise-free nights.
Although next-day cognition, cardiovascular measures, and hearing remained unaffected, participants consistently rated these nights as lower quality.
Rethinking Sleep Aids
Since sleep is so important to our overall mental health, we might need to rethink sleep aids such as broadband noise. Based on the study results, the researchers say earplugs are likely our best bet to combat noise pollution.
But despite showing an interesting trend, their study was relatively small, and the health impacts of pink noise and other ambient frequencies require deeper investigation. Overall, the evidence on the long-term effects of ambient noise on sleep quality is limited, according to a press release.
“REM sleep is important for memory consolidation, emotional regulation, and brain development, so our findings suggest that playing pink noise and other types of broadband noise during sleep could be harmful,” said study lead author Mathias Basner, professor of Sleep and Chronobiology in Psychiatry, in the release.
With millions relying on these sounds nightly, clear guidelines are important.
“Overall, our results caution against the use of broadband noise,” said Basner. “Especially for newborns and toddlers, and indicate that we need more research in vulnerable populations, on long-term use, on the different colors of broadband noise, and on safe broadband noise levels in relation to sleep.”
This article is not offering medical advice and should be used for informational purposes only
Read more: Sleep’s Surprising Role in Strengthening Long-Term Memory
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a recent study published in Sleep: Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep
