While pink noise, often touted as a sleep aid, can actually make your sleep worse by reducing REM sleep, a new study published in 2012 found that simple foam earplugs offer much better protection against nighttime noise. sleep.
Environmental noise, such as traffic, aircraft, and alarms, is known to disrupt sleep and cause long-term health problems. Deep sleep is particularly vulnerable, and chronic sleep disruption is associated with cardiovascular disease, metabolic disorders, and daytime dysfunction. At the same time, broadband noise, such as pink noise and white noise, is marketed as a way to mask unwanted sounds and promote rest. Despite the popularity of broadband noise, the scientific evidence supporting it as a sleep promoter is surprisingly thin.
Researchers led by Matthias Basner of the University of Pennsylvania designed a tightly controlled seven-day sleep experiment in 25 healthy adults (seven men) with an average age of 28.5 years. Each participant slept under different conditions, including a quiet night, a night with intermittent environmental noise (such as the sound of a car or train), a night with just continuous pink noise, and a night with a combination of environmental noise and earplugs or continuous pink noise (at two different volumes).
Each night was monitored using complete polysomnography, the gold standard for measuring sleep stages, and cognitive tests, cardiovascular measurements, audiometry, and surveys were performed in the morning.
Environmental noise alone significantly reduced deep sleep (by 23.4 minutes on average), replacing restorative deep sleep with lighter sleep stages. Interestingly, the pink noise didn’t help, instead creating its own problems. Pink noise was found to be associated with an average reduction of 18.6 minutes in REM sleep, a sleep stage important for memory, emotional regulation, and brain development.
Sleep was further disrupted when pink noise was added to the environmental noise. Participants had less deep sleep, less REM sleep, more time awake, and an overall decrease in sleep efficiency. Apparently, pink noise not only failed to protect sleep from environmental noise, but also worsened sleep architecture.
Earplugs gave completely different results. The foam earplugs used in the study restored most of the deep sleep lost to environmental noise and restored about 72% of the loss of deep sleep. On nearly every sleep measure, nights with earplugs appeared to be statistically indistinguishable from quiet control nights. Participants also reported feeling more rested and less fatigued than on nights with environmental noise (regardless of whether it was masked with pink noise or not).
The authors concluded that the negative effects of pink noise on REM sleep are a warning against widespread and indiscriminate use of broadband noise. They specifically recommended against general use in newborns and young children, noting that REM sleep is important for neurodevelopment in these age groups, although further confirmatory studies are needed.
Research has limitations. For example, this experiment was only conducted for a short period of time, only healthy young people participated, and only two levels of pink noise were tested. Real-world environments are more complex and long-term effects are still unknown.
The study, “Efficacy of pink noise and earplugs in reducing 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, and Haochang. Shaw, Cui Kao, Magdy Younes, Daniel Eschbach, and Christopher W. Jones.
