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Some people find that the neutral sound of white noise helps them sleep better. But is there evidence to support this? And what about other noise colors?

What is white noise?

White noise has been compared to the static from a radio that isn't tuned to a specific station. Technically, the term "white noise" refers to noise that contains all frequencies of the sounds that people can hear, in equal parts. (Frequency is the rate at which sound waves vibrate.)

Can white noise help you sleep better?

Studies on the benefits of white noise for sleep have yielded mixed results. Some studies have found it helped people sleep better, possibly by masking outside noises and serving as a cue to fall asleep.

"A study in infants and children showed that white noise may reduce heart rate and respiratory rate, effectively lulling an individual to sleep," says Dr. Sogol Javaheri, assistant professor at Harvard Medical School and physician in the division of sleep and circadian rhythm disorders at Brigham and Women's Hospital in Boston.

However, a published in Sleep Medicine Reviews found white noise had little beneficial effect on sleep.

What's more, according to Dr. Javaheri, white noise may interrupt important stages of sleep, such as REM sleep or deep sleep, and affect hearing if it is too loud.

If you use a white noise machine for sleep, try moving it to a corner of your bedroom and keep the noise level no louder than that of a background conversation. Turn on your white noise machine just before getting into bed. If your machine has a timer, experiment with having it play only as you fall asleep rather than all night long.

Other noise colors for better sleep: Pink noise and brown noise

While white noise is the best known, it's not the only "color" noise that's been used to enhance sleep. Pink noise has more intense, lower frequencies that make it sound deeper than white noise. Examples of pink noise are the sounds of rain or a waterfall.

Some studies have found that pink noise can enhance deep sleep in older adults and improve cognitive performance. In addition, research suggests that pink noise may decrease time to fall asleep and improve sleep quality. However, these results were achieved under experimental conditions in which researchers adjusted pink noise timing during the night.

Another color noise — brown noise — reduces higher sound frequencies even more than pink noise and is described as grainier or rougher. For example, brown noise can be compared to ocean waves crashing, while pink noise is more like a gentle rain.

"More data is needed to determine what role pink and brown noise may play in sleep, such as what volume and duration would be of most benefit," Dr. Javaheri says. "For now, I would not recommend pink or brown noise continuously, but rather use it for a set time if it helps you fall asleep more quickly."