You might think of noise as a bad thing: your neighbor’s yappy dog that wakes you up at 2 a.m. or a coworker’s radio that distracts you from your job. Yet some varieties of noise might help you sleep and work better, among other potential benefits—and they come in a rainbow of “colors.”
You might already be familiar with white noise. But have you heard about pink, brown/red, purple/violet, and blue noise?
The “color” of noise refers to the frequencies it contains and the relative intensities (loudness) of those frequencies. The names for the different colors of noise come from an analogy with visible light. So, for example, just as white light contains all the visible wavelengths from red to orange to yellow to green to blue to violet (ROYGBIV), white noise contains all the audible wavelengths of sound, from 2 to 20,000 hertz (Hz). In actuality, the analogy is rather loose and sometimes breaks down altogether, but the concept has been appealing enough to catch on.
Research is limited, but it does seem that under specific circumstances, certain “colors” can have salutary effects, at least for some people. We discuss some of them below.
White noise
As mentioned above, white noise includes the full range of frequencies in the audible spectrum of sound. If you’ve ever used a white noise machine—as nearly 1 in 10 Americans do, according to a Consumer Reports survey—you know that it gives off a sound like radio or TV static, ocean waves, heavy rain, or steam hissing from a radiator, which can help soothe you to sleep.
The broad spectrum of white noise makes it particularly good at camouflaging other ambient noises that might otherwise wake you from your slumber. White noise also promotes alpha waves, the slower and calmer brain waves that predominate when you’re relaxed, while suppressing the beta waves that rev up your brain. These dual effects (masking and soothing) may be why the preponderance of evidence about white noise centers on its ability to promote sleep and relaxation.
Indeed, research has shown benefits of white noise for helping people fall asleep faster, stay asleep longer, and sleep more soundly, making it a potentially useful nonpharmaceutical sleep aid. In one study, published in the Journal of Caring Sciences in 2016, white noise even improved the sleep quality of patients in intensive care units (ICUs), which are notoriously noisy places.
In addition, exposure to white noise has been found to improve focus and performance on tasks. In a 2017 study in Scientific Reports, for instance, white noise helped participants learn new word pairs more quickly. White noise might also have potential for calming agitated behaviors in older adults with dementia. The authors of a 2018 study that provided white noise to individuals in dementia care centers (20 minutes a day for four weeks) concluded that this “simple, convenient, and nonintrusive intervention” holds promise for improving quality of care in this population.
Pink noise
Like white noise, pink noise straddles all of the audible sound frequencies, but the higher the frequency, the lower the intensity. Because it’s more centered in the lower sound frequencies, pink noise has a steady but soothing quality, like the sound of a waterfall. Similar to white noise, pink noise masks external sounds, potentially making it helpful for improving sleep. It also appears to have a calming effect on brain waves, which could improve sleep quality.
A 2017 study published in Frontiers in Human Neuroscience suggested that exposure to pink noise during sleep boosts slow-wave activity, the phase when our brains consolidate new memories. As evidence, older adults in the study who received pulses of pink noise while they slept scored higher on tests of declarative memory (the kind of memory you use to recall specific facts and events) than those who didn’t receive pink noise stimulation.
Another, very preliminary avenue of research looked at the use of pink noise for reducing food cravings in people who were overweight. In a small study of obese women with signs of food addiction, published in Appetite in 2018, stimulating the brain with pink noise significantly reduced the women’s intense desire to eat. Pink noise reduced activity in a part of the brain called the anterior cingulate cortex. Abnormal activity in this brain region has been associated with increased food cravings.
Brown, purple, and blue noise
Brown (sometimes called red) noise, like pink noise, is more intense in the lower sound frequencies but falls off faster as the frequency increases. This gives it a sound similar to a rushing river or wind. Purple (violet) noise is the reverse of brown noise. Its volume rises along with its frequency, giving it a higher-pitched sound. Finally, blue noise is the reverse of pink noise and, like white noise, sounds like radio static (but harsher) or hissing (but hissier, so to speak).
There has been a fair amount of scientific interest in using brown, purple, and blue noise for sleep, and YouTube offers numerous mixes of these sounds for that purpose. Yet the evidence to support these three types of sounds is limited at this point.
Brown/red noise might have potential for boosting work productivity. In a study published in Noise & Health in 2020, 22 college students listened to red, pink, or white noise—or silence—and took tests of mental performance. All three of the color sounds improved productivity and helped participants feel more comfortable while they worked. However, red noise was associated with better test scores overall. The authors speculated that this type of noise might help speed the movement of messages to the cerebral cortex, which is a part of the brain responsible for thinking, learning, and remembering.
Is noise the solution?
While some colors of noise appear to improve sleep and have other benefits, research is still limited, with many studies including only small numbers of participants (as few as four to eight people) and few studies testing the different colors against one another, which makes it hard to draw firm conclusions about their effectiveness in the population as a whole. Still, there’s likely no harm in using a rainbow of sounds to try, for example, to soothe yourself to sleep, increase productivity, calm your nerves, or even ease the perception of tinnitus if you experience that—and the bottom line is that if it works for you, it works. You can find all kinds of noise colors on smartphone apps, noise machines, and YouTube videos and can experiment to see which ones suit you best.
