Pink noise is commonly used to help people fall asleep, but new research suggests it may interfere with the most restorative stages of sleep. A study from the University of Pennsylvania Perelman School of Medicine, published in the journal Sleep, found that pink noise reduced REM sleep and disrupted overall sleep recovery. In contrast, wearing earplugs proved far more effective at protecting sleep from traffic noise.
These findings call into question the growing popularity of sound machines and sleep apps that rely on continuous background noise to promote rest.
“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 study lead author Mathias Basner, MD, PhD, professor of Sleep and Chronobiology in Psychiatry.
How the Study Was Conducted
The research team monitored 25 healthy adults between the ages of 21 and 41 in a controlled sleep laboratory. Participants were given eight-hour sleep opportunities over seven consecutive nights. None reported having sleep disorders or regularly using sound to help them sleep.
During the study, participants slept under several different conditions. These included exposure to aircraft noise, pink noise alone, a combination of aircraft noise and pink noise, and aircraft noise while wearing earplugs. Each morning, participants completed cognitive tests and questionnaires designed to assess sleep quality, alertness, and other health-related effects.
Why Deep Sleep and REM Sleep Matter
During a typical night, the brain cycles repeatedly through deep sleep and REM sleep. Deep sleep plays a key role in physical recovery, memory processing, and the removal of waste products from the brain. REM sleep, often referred to as dream sleep, supports emotional regulation, motor skill development, and brain growth.
Together, these sleep stages work in balance to ensure that people wake up feeling restored and mentally prepared for the day ahead.
What Is Pink Noise?
Pink noise belongs to a category known as broadband noise. It is a continuous sound that spans a wide range of frequencies and has a steady, static-like quality. Broadband noise also includes white noise and other variations such as brown and blue noise.
Each type of noise distributes sound energy differently across the audible spectrum, which affects whether it sounds higher- or lower-pitched. Many natural sounds, including rainfall and ocean waves, fall into this category. Common household devices such as fans and air conditioning systems also produce broadband noise.
Key Findings From the Study
Compared with nights without noise, exposure to aircraft noise led to an average loss of about 23 minutes per night of “N3” sleep, which is the deepest sleep stage. Wearing earplugs largely prevented this reduction in deep sleep.
Pink noise on its own, played at 50 decibels (often compared to the sound of a “moderate rainfall”), was linked to a nearly 19-minute reduction in REM sleep. When pink noise was combined with aircraft noise, the effects were more pronounced. Both deep sleep and REM sleep were significantly shorter, and participants spent an additional 15 minutes awake during the night. This increase in wakefulness was not seen when participants were exposed to aircraft noise alone or pink noise alone.
Participants also reported that their sleep felt lighter, they woke up more often, and their overall sleep quality declined when exposed to aircraft noise or pink noise. These negative effects were largely absent when earplugs were used.
What This Means for Millions of Sleepers
The researchers said the results support the effectiveness of earplugs, which are used by up to 16 percent of Americans to help them sleep. At the same time, the findings highlight the need for more thorough research into the long-term health effects of pink noise and other broadband noise marketed as sleep aids.
Millions of people rely on continuous background noise every night. White noise and ambient podcasts alone account for three million hours of daily listening on Spotify, and the five most popular YouTube videos associated with the search term “white noise” have accumulated more than 700 million views. Despite this widespread use, studies examining how broadband noise affects sleep remain limited and often inconclusive, according to a recent review by Basner and colleagues.
Disrupted REM sleep is commonly seen in conditions such as depression, anxiety, and Parkinson’s disease. Basner also pointed out that children spend significantly more time in REM sleep than adults, which may make them especially sensitive to its disruption. Even so, many parents place sound machines near the beds of newborns and toddlers in an effort to help them fall asleep and stay asleep.
“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 and Disclosure
This study was funded by the U.S. Federal Aviation Administration Office of Environment and Energy through ASCENT, the FAA Center of Excellence for Alternative Jet Fuels and the Environment, project 86 through FAA Award Number 13-C-AJFE-UPENN under the supervision of Susumu Shirayama. Any opinions, findings, conclusions or recommendations expressed in this material are those of the investigators and do not necessarily reflect the views of the FAA.
