Are your sleep apps backfiring? Pink noise linked to poorer Rem sleep

Millions rely on sleep sounds to block night-time noise, but new research suggests pink noise may reduce Rem sleep and interfere with how the brain recovers overnight

Sleep sounds such as pink noise and white noise are widely used to block night-time disturbances and promote better rest. However, new research suggests that these popular sleep aids may not be as helpful as they appear and may even disrupt Rem sleep and undermine the brain’s overnight repair. 

A study titled Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep, published in the journal Sleep, found that pink noise reduced Rem sleep and interfered with normal sleep recovery. Conducted by researchers at the University of Pennsylvania Perelman School of Medicine, the study also showed that earplugs were significantly more effective than pink noise in protecting sleep from environmental noise such as traffic and aircraft sounds. 

The findings raise concerns about the booming market for sound machines and sleep apps, and what they might mean for long-term brain health. The study noted that white noise and ambient podcasts account for around three million hours of daily listening on Spotify, and the top five “white noise” videos on YouTube have over 700 million views. 

Why are sleep sounds so popular? 

Sleep sounds are marketed as an easy fix for restless nights. From newborn nurseries to adult bedrooms, background noise is often used to mask sudden environmental sounds that can wake people up. 

Pink noise, in particular, is promoted as gentler and more “natural” than white noise. Many people believe it helps the brain relax, fall asleep faster, and stay asleep longer, especially in noisy environments. It contains sound across many frequencies. Unlike white noise, which emphasises higher frequencies, pink noise distributes sound energy more evenly, giving it a softer, deeper tone. 

Common examples include: 

• Steady rainfall 
• Ocean waves 
• Wind through trees 
• The hum of fans or air conditioners 

Because of its calming quality, pink noise is widely used in sleep apps, sound machines, and even hospital settings. 

What did the study find about pink noise and sleep quality? 

According to the research paper, to understand how pink noise affects sleep, researchers studied 25 healthy adults aged 21 to 41 in a controlled sleep laboratory. 

Each participant slept eight hours per night for seven consecutive nights, had no sleep disorders, and did not regularly use sleep sounds. They experienced different night-time conditions, including: 

• Aircraft noise alone 
• Pink noise alone 
• Aircraft noise combined with pink noise 
• Aircraft noise while wearing earplugs 

Every morning, participants completed tests measuring sleep quality, alertness, and cognitive performance. 

The researchers found: 

• Aircraft noise reduced deep sleep by about 23 minutes per night, and wearing earplugs largely prevented this loss
• Pink noise alone was linked to nearly 19 fewer minutes of Rem sleep 
• Pink noise combined with aircraft noise had the worst effects, causing significant loss of both deep sleep and Rem sleep, about 15 extra minutes awake during the night, and poorer perceived sleep quality

Participants reported lighter sleep, more frequent awakenings, and overall worse rest during nights with pink noise or aircraft noise.

Why deep sleep and Rem sleep are critical for the brain 

According to the researchers, deep sleep supports physical recovery, immune function, and memory consolidation, while Rem sleep, often associated with dreaming, plays a vital role in emotional regulation, learning, creativity, and brain development. 

These stages work together to restore the brain and body. Disrupting either can leave people feeling foggy, emotionally off-balance, and less resilient to stress. 

The researchers emphasise that losing Rem sleep is particularly concerning because it is essential for: 

• Memory consolidation 
• Emotional stability 
• Motor skill learning 
• Brain development 

The authors highlighted that disruptions to Rem sleep are commonly seen in conditions such as depression, anxiety, and Parkinson’s disease. 

Earplugs outperform sleep sounds in protecting rest 

The study found that earplugs provided better protection against environmental noise without interfering with natural sleep architecture. Unlike continuous sound, earplugs reduced noise exposure without introducing an additional auditory stimulus that the brain must process throughout the night. 

Should parents worry about sleep sounds for children? 

The study urges caution, especially for newborns and toddlers, as they are more vulnerable. They spend significantly more time in Rem sleep than adults, yet sound machines are often placed near infants’ and toddlers’ beds to help them sleep. 

The authors stress that masking noise is not the same as protecting sleep, and when it comes to healthy rest, less stimulation may be better than more.