Listening to music and certain types of sounds have shown to improve sleep, promote relaxation, and distract the mind from other ambient sounds such as traffic or rowdy neighbors. Research suggests that "pink noise" may help improve sleep and memory — but most of us have only heard of white noise. What’s the difference, and why should we care?
The benefits of white noise for sleep
When it comes to drowning out unpleasant sounds from the environment, white noise can work well as a way to mask sudden sounds that may otherwise jolt you awake during the night.
White noise is a consistent, even sound emitted across all audible frequencies. Since this sound is constant, it can help drown out and reduce the effect of other sounds in the environment, particularly ones that occur suddenly (such as a car horn honking or shouting from late-night revelers).
These benefits have led to the proliferation of white noise machines — although cheaper alternatives such as running a fan or tuning the radio to a frequency that emits nothing but static may be just as beneficial.
So what is pink noise?
Pink noise emphasizes lower frequencies and occurs more frequently in nature. Whereas white noise sounds like radio static, pink noise sounds more like rushing water. It is often used in audio engineering and is thought to be a more natural sound to listen to when compared to white noise.
The relationship between memory and sleep
As we age, we are more likely to experience memory loss. Since adequate sleep may help battle cognitive decline it makes sense to consider that improving sleep may have a positive effect on memory — and a 2017 study published in Frontiers in Human Neuroscience suggested that pink noise may help improve both sleep and memory.
Researchers recruited 13 participants over the age of 60. Each received one night of exposure to pulses of pink noise and one night without exposure to pink noise. Participants took a memory test at night and in the morning following each night of sleep monitoring. Sleep was measured using polysomnography.
Researchers found that when participants were not exposed to pink noise, memory improved on the morning test by a few percentage points. However, the improvement was three times larger when participants were exposed to pink noise.
The study also found that when participants were exposed to pink noise during sleep, there was an increase in slow brainwaves. This suggested that participants enjoyed longer periods of deep sleep when pink noise was played.
A few words of caution
Before you rush out to buy pink noise audio sessions, it’s worth highlighting the scientific processes involved in this research. Participants didn’t actively listen to the pink noise since the sound pulses were played only when participants were already asleep.
Researchers monitored participants in a laboratory and only played the pink noise when they saw an increase in slow brainwaves — a sign that participants were in the deep sleep stage (also known as slow wave sleep). The pink noise was also played in a series of short bursts that were spaced out so the brain wouldn’t get used to the sound and end up filtering it out.
As a result, it is going to be difficult to replicate these results at home. Although more studies are needed on how pink noise influences sleep and memory — and whether these results can be replicated over the long term — Northwestern University in Chicago has a patent pending for the technology and is looking to develop a consumer device that can be used at home.
With that being said, older studies have found that playing continuous pink noise can help when it comes to falling asleep — so having pink noise play in the background at night may still be helpful in promoting relaxation and helping to drown out environmental noises that can make sleep more difficult.