The Woolcock Institute of Medical Research

In a recent Radio 2SM interview, Woolcock sleep psychologist and insomnia specialist Professor Delwyn Bartlett spoke to journalist Brent Bultitude about new research indicating that pink noise – increasingly promoted as a sleep aid – may actually reduce some of the most important stages of sleep.

Pink noise is a type of continuous broadband sound that spreads across a wide range of frequencies. Like white and brown noise, it is often described as a steady, static-like background sound, but with a different frequency balance that gives it a deeper, more even tonal quality. It is commonly marketed through sleep apps and online platforms as a tool to improve sleep quality and stability.

However, new findings from researchers at the University of Pennsylvania suggest the effect may not be beneficial. In a controlled laboratory study, 25 healthy adults completed seven nights of monitored sleep under different sound conditions, including environmental noise, pink noise and combinations of noise exposure with earplugs. Participants also completed cognitive, cardiovascular and hearing tests in the morning to measure next-day effects.

TOO IMPORTANT TO LOSE

The results showed that while environmental noise – such as aircraft or traffic sounds – predictably disrupted deep sleep, adding pink noise did not correct the problem. Instead, pink noise exposure was associated with reductions in both deep sleep (also known as slow-wave or N3 sleep) and REM sleep.

“We don’t really want to lose a lot of it,” said Professor Bartlett because these stages play a central role in physical and mental restoration. Deep sleep supports body repair and growth hormone release, while REM sleep is strongly linked to memory consolidation and emotional processing. Together they make up less than half of total sleep time, so even modest reductions can be meaningful. A loss of 15-20 minutes of REM sleep per night is considered significant in clinical sleep research, roughly comparable to the total sleep-time gains seen with some insomnia medications.

Normal sleep occurs in cycles of about 90 minutes. Deep sleep is concentrated in the first part of the night, while REM periods lengthen toward morning. It is therefore common for people to wake after several hours of sleep, particularly as lighter sleep and REM become more dominant. This pattern can be misinterpreted as insomnia when it is often a normal shift in sleep architecture.

“When we get three hours of sleep or a little bit longer, we need to change our expectations of our sleep,” said Professor Bartlett. “We need to expect that we’re going to wake more frequently and that we’re going to have more very light sleep and a bit of dreaming.”

LEARNING BETTER SLEEP

Professor Bartlett noted that while background sound can sometimes help mask disruptive environmental noise, people should be cautious about relying on any single audio stimulus as a long-term sleep solution.

“It’s really important for us to be able to learn to sleep on our own,” she said. “To let go of the day and to know that we can’t have a good night’s sleep every night – but that’s okay as long as we set good boundaries around it.”

White noise or natural sounds such as gentle rain or ocean waves may be reasonable options in noisy settings, but building independent sleep skills remains important.

Behavioural approaches – including daytime breathing practice and techniques such as paradoxical intention, where individuals reduce sleep performance pressure by briefly trying to stay awake – can also help manage middle-of-the-night awakenings.

Overall, the emerging evidence suggests that newer sound-based sleep trends, including pink noise, should be evaluated carefully, with attention to their effects on the most biologically important stages of sleep.

In the end, says Professor Bartlett, “We all need things to help us sleep along the way depending on what’s happening in our lives.”

Find out more

• Our Insomnia Clinic
• Learning Better Sleep
• Relaxation Strategies for Insomnia