The Sleep Sound Millions Trust May Be Stealing Your REM Sleep

Sound machines and “sleep sounds” are often marketed as a cure for restless nights, but new research suggests they may actually be working against the brain.

Pink noise is widely used to help people sleep, but new research suggests it may interfere with the brain’s ability to recover overnight. 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 sleep recovery. In comparison, earplugs provided far better protection against traffic noise during sleep.

The findings raise concerns about the growing use of sound machines and apps that rely on continuous background noise as sleep aids.

“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 Designed

The research team studied 25 healthy adults aged 21-41 in a controlled sleep laboratory. Each participant was given eight hours to sleep each night over seven consecutive nights. None of the participants reported sleep disorders or regular use of noise to help them sleep.

Participants slept under several different conditions. These included exposure to aircraft noise, pink noise alone, aircraft noise combined with pink noise, and aircraft noise while wearing earplugs. Each morning, participants completed tests and surveys that measured sleep quality, alertness, and other health related effects.

Why REM Sleep and Deep Sleep Matter

During sleep, the brain repeatedly cycles through deep sleep and REM sleep. Deep sleep supports physical recovery, memory consolidation, and the removal of toxins from the brain. REM sleep, often referred to as dream sleep, plays a key role in emotional regulation, motor skill development, and brain growth.

Together, deep sleep and REM sleep work in balance to help the body and brain recover, allowing people to wake up feeling restored and prepared for the day.

What Pink Noise Is

Pink noise is a form of broadband noise. It produces a steady sound across many frequencies and has a uniform, static-like quality. Other types of broadband noise include white noise and additional sound variations such as brown and blue noise.

These noise types differ in how sound energy is distributed across the audible spectrum, which affects whether they sound higher or lower in pitch. Many natural sounds, including rainfall and ocean waves, fall into the broadband noise category. Common household devices such as fans and air conditioning systems also generate broadband noise.

What the Researchers Found

Compared with nights without noise, exposure to aircraft noise was linked to an average loss of about 23 minutes per night of “N3,” the deepest stage of sleep. Wearing earplugs largely prevented this reduction in deep sleep.

Pink noise played on its own at 50 decibels (often compared to the sound of a “moderate rainfall”) was associated with nearly 19 fewer minutes of REM sleep. When pink noise was combined with aircraft noise, the effects were more severe. Both deep sleep and REM sleep were significantly reduced, and participants spent about 15 additional minutes awake during the night. This increase in wake time did not occur during nights with 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 during nights with aircraft noise or pink noise. These negative effects were largely avoided when participants used earplugs.

What This Means for Everyday Sleep Habits

The researchers said the results suggest that earplugs, which are used by as many as 16 percent of Americans to help them sleep, are likely effective. At the same time, the findings point to the need for more research on the potential health effects of pink noise and other broadband noise marketed as sleep aids.

Millions of people use broadband noise every night. White noise and ambient podcasts alone account for roughly three million hours of daily listening on Spotify, and the top five YouTube videos associated with the search term “white noise” have accumulated more than 700 million views. Despite this widespread use, research on how broadband noise affects sleep remains limited and often inconclusive, according to a recent review by Basner and colleagues.

Disruptions in REM sleep are commonly seen in conditions such as depression, anxiety, and Parkinson’s disease. Basner also noted that children spend significantly more time in REM sleep than adults, which may make them especially sensitive to its disruption. Even so, it is common for parents to 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.

Reference: “Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep” 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, Haochang Shou, Quy Cao, Magdy Younes, Daniel Aeschbach and Christopher W Jones, 2 February 2026, Sleep.
DOI: 10.1093/sleep/zsag001

This research 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.

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