That Soothing Sleep Noise Might Be Sabotaging Your Dreams

Many of us use soft background noise to help us fall asleep and keep us there. Unfortunately, this strategy could actually backfire in a big way, new research finds.

Scientists at the University of Pennsylvania studied people as they tried to sleep under a variety of noise conditions, including pink noise. Compared to no sound at all, people dozing off with pink noise experienced noticeable drops in how much REM sleep they got, the researchers found. It also appeared to be woefully ineffective at counteracting the harmful effects of other loud sounds on sleep, especially compared to earplugs.

“While more studies on the long-term use of [broadband noise] are needed, these findings caution against its indiscriminate use, especially in newborns and toddlers for whom REM sleep is critical for neurodevelopment,” the researchers wrote in their paper, published Monday in the journal Sleep.

Counterproductive noise

Pink and similar noises, like white and brown, are called broadband noises. These are continuous streams of noise spread across a wide range of frequencies but differ by how much energy is distributed in those frequencies. Pink in particular sounds like a soft waterfall, waves crashing, or other gentle nature noises (an example can be heard here).

People often claim that broadband noises have various health benefits, such as drowning out abrasive sounds as well as promoting healthy and well-rested sleep. But according to the authors, the research on how broadband noise can affect sleep is decidedly mixed. A 2021 review from the same team found only weak evidence supporting the idea that it can help sleep, and some studies even pointed to possible harms.

“My research focuses on the negative effects of traffic noise on sleep,” lead study author Mathias Basner, a professor of sleep and chronobiology in psychiatry at UPenn’s Perelman School of Medicine, told Gizmodo. “I was confused when I heard that people would introduce a noise source into their bedroom to help them sleep.”

To study the effects of pink noise for themselves, they recruited 25 healthy adults (ages 21 to 41) for a week-long experiment. The researchers observed the volunteers trying to sleep over an 8-hour period each night, though with different noise stipulations. These included listening to aircraft noise alone, pink noise alone (at 50 decibels), aircraft noise plus pink noise (one night each at 40 or 50 decibels), and aircraft noise while wearing earplugs. No noise was the control condition.

Understandably, people had a rougher night while listening to aircraft noise. On average, compared to no noise, they obtained roughly 23 fewer minutes per night of N3 sleep, the deepest stage of sleep. But even pink noise seemed to have a negative impact. Under this condition, the researchers found, people had about 19 fewer minutes of REM sleep, the stage of sleep associated with vivid dreaming and the consolidation of our memories.

Perhaps more surprisingly, the combination of aircraft and pink noise might have been the worst of all. Not only did people under this condition still experience drops in both REM and deep sleep, but they also spent roughly 15 minutes longer being awake. Volunteers also reported an overall poorer quality of sleep when listening to the combination of aircraft and pink noise. That said, the negative effects of aircraft noise were largely abated when the volunteers wore earplugs.

Should you sleep with pink noise on?

The findings are still based on a small sample size. So it will take more studies to conclusively confirm the effects that pink and other broadband noises are having on people’s sleep, especially when used for a long time.

“Pink noise helped a little bit improving deep sleep and reducing sleep fragmentation (i.e., waking up to environmental noise). So, it’s not all bad,” Basner noted. “Therefore, it is still hard to say what the long-term consequences would be, especially since we don’t have data on long-term use.”

At the same time, the widespread popularity of these sounds as a sleep and relaxation aid—Spotify users alone spend millions of hours listening to white noise every day—certainly doesn’t seem justified given the evidence to date, the researchers argue. They also advise that very young children in particular should avoid any kind of noisy bedtime sounds for the time being, since they spend much more time in REM sleep (up to 50% of the night for newborns).

Basner and his team are now planning a follow-up study that will study different types of broadband sounds and noise levels, in hopes of finding the optimal combination for promoting a good night’s sleep. Meanwhile, I’m just really hoping science’s next target isn’t that warm glass of milk.

This article has been updated with comments from one of the study’s authors.