A study from the University of Pennsylvania Perelman School of Medicine challenges the widespread use of ambient sound machines, finding that pink noise may reduce restorative REM sleep and interfere with sleep recovery. The research shows earplugs work better than noise machines in protecting sleep from aircraft noise, potentially affecting millions who use sound apps nightly.

Researchers observed 25 healthy adults in a sleep lab over seven nights, testing different noise conditions. Results revealed aircraft noise reduced deep sleep by approximately 23 minutes, while pink noise decreased REM sleep by nearly 19 minutes. When combined, both deep and REM sleep suffered significantly, with participants reporting lighter sleep and more frequent awakenings.

The findings suggest common sleep aids could be particularly harmful to children, who spend more time in REM sleep than adults. Dr. Mathias Basner, lead author, cautions against using broadband noise machines for newborns and toddlers, calling for more research on long-term effects and safe noise levels for vulnerable populations.