You have probably heard of white noise, which is thought of as comforting sounds that help us block out the surrounding environment, like a fan humming away just loud enough that we don’t really hear doors closing or a dog barking outside. In more technical terms, white noise is a random signal that has an equal intensity at different frequencies. White noise is like white light, which contains all visible light at an equal intensity. Fracture that light, and you get a rainbow.
Sound engineer Stéphane Pigeon explains white noise as “hundreds of musicians playing every single note you can hear at once at the same volume.”
What Is Pink Noise?
Pink noise is a soothing, gentle sound composed of octaves possessing equal energy. In white noise, the power of each frequency is constant, but in pink noise, as frequencies get higher, the difference in power of the associated sounds becomes smaller. The effect is that higher-pitched sounds are softer.
This is essentially the nature of background noise we are used to hearing every day. High-pitched sound waves don’t carry as far and are more easily absorbed by whatever they land against, while lower-pitched sounds can penetrate through and carry further. This is why you can hear the bass of a passing car’s stereo more easily than the treble. Pink noise emulates the normal pattern of sounds in our environment.
It turns out, this aspect of pink noise has benefits.
Researchers at Northwestern University in Evanston, Illinois, discovered that if they synced pink noise to the brain waves of older men and women while they slept, the subjects experienced better quality of deep sleep as well as an improvement in memory.
“During sleep, a real-time algorithm using an adaptive phase-locked loop modeled the phase of endogenous slow waves in midline frontopolar electroencephalographic recordings,” wrote the researchers, explaining how they synced the noise to the participants’ brainwaves. The study was published in The Frontiers of Neuroscience in 2017.
Essentially, they used a machine to monitor brain waves and adjusted the sound to match.
It’s been shown in numerous studies over the years that sleep is critical for converting short-term memories into long-term memories. The type of sleep necessary for this conversion is deep sleep, aka slow-wave sleep or non-dream-state sleep, which is part of the non-rapid eye movement sleep cycle. As we get older, the quality of deep sleep declines, which in turn can have a significant impact on memory as well as sleep quality.
Deep sleep is also important because it’s the stage when the body’s cells increase production, and there’s a reduction in the breakdown of proteins. Thus this is a time of tissue repair, giving meaning to the term “beauty sleep.” Other benefits of deep sleep are a slowing of activity in the areas of the brain involved with emotions, social engagement, and decision-making, which suggests that deep sleep helps people maintain an emotional balance.
How Scientists Used Pink Noise
Previous studies in young adults found a link between acoustic (sound) stimulation of deep sleep brain activity and an improvement in memory. These findings prompted Dr. Phyllis Zee, professor of neurology at the Feinberg School of Medicine at Northwestern, and her colleagues to try acoustic stimulation in a group of older adults to see how it affected sleep and memory.
The study group consisted of 13 men and women ages 60 to 84 who each were subjected to one night of acoustic stimulation (involving pink noise synced to the participants’ brain waves) and one night of sham (placebo) stimulation. Each of these sessions were conducted one week apart. Before and after each of the sessions, the participants completed two memory recall tests.
The researchers found that:
- Memory recall was three times better after acoustic stimulation with pink noise than it was with the placebo stimulation.
- The improvement in memory correlated with a boost in the quality of deep sleep and therefore an improvement in sleep quality.
Dr. Zee stated that the use of acoustic stimulation with pink noise “is an innovative, simple, and safe non-medication approach that may help improve brain health.” Use of pink noise could be a “potential tool for enhancing memory in older populations and attenuating normal age-related memory decline.” The next step is to use this approach over a longer time period and in in-home environments.
Deborah Mitchell is a freelance health writer who is passionate about animals and the environment. She has authored, co-authored, and written more than 50 books and thousands of articles on a wide range of topics. This article was originally published on NaturallySavvy.com