‘Pink Noise’ Could Be Harming Your Sleep Quality, Study Warns

The soothing sounds of pink noise, designed to obscure outside clamor and lull listeners into sleep, may not be so innocuous, a new study suggests.

Researchers at the University of Pennsylvania, with their collaborators in Europe and Canada, have found that pink noise, a sound palette touted as a sleep aid, may actually harm sleep quality.

Pink noise is one type of broadband noise, a term for continuous sounds spread across a range of frequencies. White noise is perhaps the most famous of these sonic hues, but there is also brown noise, blue noise, and others. Each one differs in the intensity of sound waves at different frequencies.

White noise is a popular sleep aid, commonly used for masking environmental noise or tinnitus. Research has yielded mixed results, suggesting it may help in some contexts but also pointing to potential risks.

Pink noise, with its greater intensity at lower frequencies, comes across as softer and less staticky than white noise, often drawing comparisons to the sound of rain or a waterfall. Many ambient-sound apps and devices promote it as a sleep aid, but the new findings raise questions about those claims.

Researchers recruited 25 adults for the study, ranging in age from 21 to 41, with no sleeping disorders or history of using noise as a sleep aid. These participants spent seven consecutive nights in a sleep lab, trying to sleep for 8 hours under varying conditions as the researchers observed.

After one noise-free night to adapt to their new quarters, participants were exposed to a different sonic condition each night. The sequence varied between groups.

One night they heard a mix of environmental noises, including passing aircrafts, vehicles, and a baby crying; another night they listened to just pink noise. The other nights they had a quiet control night or slept with environmental noise plus pink noise or environmental noise plus earplugs.

The participants filled out surveys rating their sleep and completed cognitive and cardiovascular tests before and after each night, to add to the data collected while they slumbered.

Compared with noiseless nights, sleepers exposed to a barrage of environmental noise spent an average of 23 fewer minutes per night in N3 sleep, the deepest stage of sleep.

Pink noise on its own at 50 decibels was also associated with nearly 19 fewer minutes of REM sleep per night compared to environmental noise.

On nights with environmental and pink noise, both REM and deep sleep were significantly shorter than on quiet control nights, the researchers found. Participants also spent more time awake on the nights with both noises, which didn’t happen with either sound alone.

Overall, sleep quality seemed to suffer on the noisier nights, including those with pink noise. There was one exception, however: noisy nights with earplugs.

People wearing earplugs didn’t exhibit the same sleep differences on nights with pink noise, environmental noise, or both, suggesting earplugs may offer a safer alternative to broadband sound.

While this lab study may only be small, the findings cast doubt on the supposed benefits of using pink noise to help with sleep, especially given what we know about importance of REM and deep sleep for brain health, says University of Pennsylvania sleep researcher Mathias Basner.

Related: Sleepless Nights Could Drive Half a Million Cases of Dementia in The US Each Year

“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 – especially for children whose brains are still developing and who spend much more time in REM sleep than adults,” Basner says.

Millions of people play broadband sounds as they sleep, and while it may help some, the research so far is inconclusive – and there is enough evidence to at least warrant caution, the researchers note.

“Overall, our results caution against the use of broadband noise, 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,” Basner says.

The study was published in Sleep.