SLEEPLESS NIGHTS?: It could be ‘pink noise’ disrupting your rest
A study from the University of Pennsylvania Perelman School of Medicine found that pink noise, a common sound produced by sleep machines and often described as moderate rainfall at 50 decibels, can reduce REM sleep.
Researchers tested 25 healthy adults aged 21 to 41 who did not use noise machines and had no sleep disorders. Over seven nights in a sleep lab, participants were exposed to aircraft noise, pink noise, a combination of both, and aircraft noise with earplugs. Aircraft noise alone reduced deep sleep by about 23 minutes. Pink noise alone decreased REM sleep by nearly 19 minutes. The combination of aircraft noise and pink noise reduced both REM and deep sleep stages and increased time awake by 15 minutes compared with quiet nights.
Participants reported that sleep felt lighter, of worse overall quality, and involved more frequent awakenings when exposed to aircraft or pink noise, unless earplugs were used. Earplugs largely prevented the loss of deep sleep from aircraft noise and improved perceived sleep quality. Pink noise mitigated some of the reduction in deep sleep and sleep fragmentation caused by intermittent environmental noise.
Lead author Mathias Basner, M.D., Ph.D., noted that playing pink noise and other broadband noise during sleep could be harmful, especially for children whose brains are still developing and who spend more time in REM sleep than adults. He added that pink noise may be beneficial for individuals with primary sleep problems such as low deep sleep and sleep fragmentation. Sleep expert Dr. William Lu stated that pink noise masks external disruptions but introduces a constant auditory stimulus that fragments and reduces REM sleep, which is important for memory consolidation, emotional regulation, and brain development. Deep sleep supports physical restoration and toxin clearance.
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The study, published in the journal Sleep and funded by the FAA, recommends caution with broadband noise, particularly for newborns and toddlers, until more research is conducted. If pink noise is used, it should be at the lowest effective volume and placed on a timer to turn off after falling asleep. Earplugs proved more effective at blocking traffic noise and improving sleep quality. The researchers called for further studies on long-term effects, different colors of broadband noise, and safe volume levels, especially in vulnerable populations. The small, short-term study did not examine individual differences or extended use.