A recent study from the University of Pennsylvania Perelman School of Medicine has found that pink noise, commonly used to aid sleep, may actually reduce restorative REM sleep and interfere with overall sleep recovery. The research, published in the journal Sleep, also indicates that earplugs are more effective than pink noise in protecting sleep against traffic-related disturbances.
The use of ambient sound machines and apps as sleep aids is widespread. However, the study’s findings challenge their effectiveness and safety. “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,” said Mathias Basner, MD, PhD, professor of Sleep and Chronobiology in Psychiatry at Penn Medicine.
Researchers observed 25 healthy adults aged 21 to 41 in a controlled laboratory setting over seven consecutive nights. Participants had no prior history of using noise to help them sleep or any diagnosed sleep disorders. They experienced various conditions: exposure to aircraft noise alone, pink noise alone, aircraft noise combined with pink noise, and aircraft noise with earplugs. Each morning they completed tests and surveys on their perceived quality of restfulness and alertness.
Sleep consists of cycles between deep (N3) and REM stages. Deep sleep supports physical restoration and toxin clearance from the brain; REM is crucial for emotional regulation and cognitive functions such as memory consolidation.
Pink noise is a type of broadband sound characterized by a consistent static-like tone spread across many frequencies. It includes sounds like ocean waves or rainfall as well as household appliances such as fans or air conditioners.
The study found that exposure to aircraft noise resulted in about 23 fewer minutes per night spent in deep N3 sleep compared to quiet nights; however, earplugs largely prevented this reduction. Pink noise played at 50 decibels led to nearly a 19-minute decrease in REM sleep per night. When both aircraft and pink noises were present together, participants experienced shorter periods of both deep and REM sleep along with an increase in time spent awake by about 15 minutes compared to control nights without added sounds.
Participants reported lighter overall restfulness, increased awakenings during the night, and poorer subjective quality when exposed to either aircraft or pink noises unless they wore earplugs.
The researchers noted that while up to 16 percent of Americans use earplugs for sleeping purposes—which appear effective—the potential negative health impacts from routinely using broadband noises like pink or white noise require further investigation. Millions regularly play these sounds at bedtime: white-noise podcasts alone account for three million daily hours on Spotify’s platform; top YouTube videos related to “white noise” have amassed over 700 million views globally.
Research into how these popular sound aids affect human health remains limited. Disrupted REM cycles are associated with disorders including depression, anxiety, and Parkinson’s disease. Young children may be especially vulnerable since they spend proportionally more time in REM phases—and it is common practice for parents to place sound machines near infants’ beds intending better rest.
“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 said.
Funding for this work was provided by the U.S. Federal Aviation Administration Office of Environment and Energy through ASCENT under FAA Award Number 13-C-AJFE-UPENN supervised by Susumu Shirayama. The conclusions represent those of the investigators rather than official FAA positions.
