Your brain stays alert while sleeping

Even during sleep, your brain monitors the outside world through sounds and smells. This makes evolutionary sense: your brain needs to detect potential danger.

Some sounds deepen sleep

Researchers at MIT played pink noise to sleeping people in an MRI machine and observed cerebrospinal fluid pulsing in response, suggesting the sound could improve sleep quality.

Brain fluid clears waste during sleep

Scientists believe cerebrospinal fluid flowing around the brain removes biochemical waste products during sleep, which may be why sleep feels restorative. Large waves of fluid pulse through the brain when people fall asleep.

Pink noise vs white noise

Pink noise is similar to white noise but lower-pitched and more even sounding, making it less harsh. A 2013 study found pink noise improved memory performance the next day, though later findings have been mixed.

“It's less harsh-sounding than static white noise that people might be familiar with.”

Timed bursts amplify brain waves

Researchers developed an algorithm to play 50 millisecond bursts of pink noise precisely when slow brain waves peaked during sleep. This amplified slow waves and increased cerebrospinal fluid flow into the brain.

Next: treating sleep disorders

The discovery opens doors to studies testing whether boosting cerebrospinal fluid flow could help people with poor sleep or neurodegenerative conditions caused by impaired brain waste removal. A wearable device is in development.