Research shows the mix of high and low frequency sounds in pink noise can deepen sleep and improve memory.
Sweet dreams are made of pink.
Most people are familiar with listening to white noise — like the steady hiss of TV or radio static — to mask distracting car alarms or barking dogs when you’re trying to sleep. But now “pink noise” — a more natural-sounding mix of high and low frequencies — is getting buzz as research suggests it supports deeper sleep and better memory.
Dr. Roneil Malkani, assistant professor of neurology at Northwestern University, told Moneyish that we assign colors to sound the same way that we do with light. So white noise is a combination of all the other sound waves (violet, blue, white, pink and brown/red) the same way white light is made up of all the colors of the rainbow.
“When all of those various sound frequencies are equally represented, you get white noise,” he explained, which is why it makes a constant static or “shhhh” sound.
But pink noise is all about that bass. “Pink noise is very similar to white noise, but it’s shifted toward the lower end of the spectrum,” said Dr. Malkani. “The sound pulses and has more bass in it.” Which is why pink noise is likened to rainstorms, or sometimes rumbling traffic — which you may have even considered white noise before.
Dr. Malkani’s colleagues at Northwestern University have been studying whether pink noise can enhance sleep because the frequency of pink sound waves is actually very similar to that of our brain waves during stage 3 slow wave sleep — which is also the sleep stage linked to memory processing, particularly remembering facts.
They’ve been mostly experimenting on older subjects, because deep sleep decreases sharply in middle age, which scientists suspect contributes to memory loss in aging. So Northwestern’s most recent pink wave study had 13 adults in their 60s and up take a memory test on two nights before sleeping in the lab, waking up, and taking the same memory test (which called for remembering pairs of related words) the next morning. On one night, they were given “soft, short bursts of pink noise when the slow brain waves were present,” explained Dr. Malkani, “to see if it enhanced the slow waves there.” On the other night, they didn’t receive the pink noise at all. And their deep sleep waves were not only longer during the pink noise night, but the subjects also recalled almost three times more words during the memory test the next morning than they did after the night without the noise.
This backs a similar study done with people napping in 2016, which also found that those who listened to pink noise in their sleep had deeper sleep and better memory recall. And a 2012 study in China tested pink noise an adult subjects during both nighttime sleep and daytime naps, and while they found the subjects had deeper sleep in the evening, there was an even greater improvement with their daytime napping when they listened to pink noise.
So pink noise could be a dream for the three in four chronically sleep deprived workers who snooze less than the recommended seven to nine hours a night, according to a recent Glassdoor report. And workers getting insufficient sleep costs the U.S. economy $411 billion in lost worker productivity.
But before you go downloading pink noise apps to ace a test or cure your insomnia, it should be noted that these studies were held under very controlled circumstances where the sounds were played at just the right moments. “We monitor what the brain waves are doing so we can deliver the sound when there are slow waves, and to my knowledge, there is no app or product available that would actually do that yet,” said Dr. Malkani. The end goal is to eventually have something consumers can wear at home at night as a potential sleep therapy, but that’s still years away.
In the meantime, there are apps and sound machines that now play pink noise to help you sleep; just don’t expect to get the same results these scientists saw in their labs. But you can experiment listening to pink noise while zoning out on your own with apps such as Noisli ($1.99 on iTunes and Google Play) a background noise generator which lets you combine pink noise sounds like falling rain and rolling thunder to create your ideal soundtrack. Simply Noise (99 cents on iTunes and Google Play) lets you pick from different color orbs, including pink, to find the frequency that’s the most musical to your ears. Playnoise.com also features free pink, brown, blue and white noise frequencies. And many sound machines running for $20 to $80 on Amazon feature pink noise among their frequencies.
© 2018 Dow Jones & Company, Inc. All Rights Reserved