A new study raises questions about the use of “pink noise” devices, which are common among those seeking to improve sleep quality. According to the study’s findings, sounds perceived as calming and sleep-promoting may negatively affect brain activity and essential sleep stages.
Pink noise devices are electronic means that emit broad sound frequencies, covering the entire range of human hearing. The sounds resemble natural noises such as flowing water, raindrops, or rustling leaves, and are intended to create a sense of calm and assist with falling asleep and deep sleep.
The study was conducted by a team of researchers from the Perelman School of Medicine at the University of Pennsylvania. As part of the experiment, a team of 25 adults stayed for seven nights in a dedicated sleep research laboratory. During the nights, participants were exposed to different stimuli: Airplane noise, pink noise, or alternatively sleep with earplugs. The researchers measured sleep depth and the participants’ level of concentration after waking.
Damage to deep sleep and REM
The study’s findings, published in the scientific journal Sleep, showed that exposure to airplane noise causes a loss of approximately 23 minutes of deep sleep each night – a stage in which the brain clears metabolic waste that accumulates during the day. In contrast, the use of earplugs prevented damage to this stage.
It was further found that pink noise reduces the duration of the sleep stage known as REM (Rapid Eye Movement) by approximately 19 minutes – a stage characterized by intensive brain activity, dreams related to emotional processing, development of motor skills, and brain development. The stage received its name due to the rapid eye movements that occur beneath the closed eyelids.
When participants were exposed to both airplane noise and pink noise simultaneously, an even sharper decline in sleep quality occurred: Deep sleep duration and the REM stage were shortened, and the subjects remained awake for longer periods before falling asleep.
Concern about impact on children
On the medical website HealthDay, the head of the research team was quoted as saying that the findings indicate that listening to pink noise or similar broad-spectrum sounds may be harmful to health. According to him, the risk is particularly significant among children, whose brains are still in the process of development and who spend a greater portion of their sleep time in the REM stage compared to adults.
The researchers emphasize that despite the popularity of pink noise devices, further research is needed to fully understand their long-term impact on sleep and brain health.