You may have heard of white noise used to mask background sounds. Now, it has colorful competition.

There害羞草研究所檚 a growing buzz around pink noise, brown noise, green noise 害羞草研究所� a rainbow of soothing sounds 害羞草研究所� and their theoretical effects on sleep, concentration and the relaxation response.

The science is new with only a few small studies behind it, but that hasn害羞草研究所檛 stopped thousands of people from listening to hours of these noises on YouTube and on meditation apps that provide a palette of color noises with paid subscriptions.

WHAT IS PINK NOISE?

To understand pink noise, start with white, the most familiar of the color noises.

White noise is similar to static on a radio or TV. Sound engineers define it as having equal volume across all the frequencies audible to the human ear. It gets its name from white light, which contains all the visible color wavelengths.

But the high frequencies of white noise can sound harsh. Pink noise turns down the volume on those higher frequencies, so it sounds lower in pitch and more like the natural sound of rain or the ocean.

Brown noise sounds even lower in pitch, giving it a pleasing, soothing rumble.

Pink and brown, like white, have standard definitions to audio experts. Other color noises are more recent creations with very flexible definitions.

WHAT害羞草研究所橲 THE SCIENCE BEHIND COLOR NOISES?

White noise and pink noise may provide small benefits for people with attention-deficit/hyperactivity disorder, according to a recent review of limited ADHD studies. In theory, it wakes up the brain, said ADHD researcher and co-author Joel Nigg of Oregon Health & Science University in Portland.

害羞草研究所淭he noise provides stimulation to the brain without providing information, and so it doesn害羞草研究所檛 distract,害羞草研究所� Nigg said.

White noise has been used to treat ringing or buzzing in the ear, called tinnitus.

Scientists at Northwestern University are studying how short pulses of pink noise can enhance the slow brain waves of deep sleep. In small studies, these pink-noise pulses have shown promise in improving memory and the relaxation response.

Pink noise has a frequency profile 害羞草研究所渧ery similar to the distribution of brain wave frequencies we see in slow-wave sleep because these are large, slow waves,害羞草研究所� said Dr. Roneil Malkani, assistant professor of neurology at Northwestern University Feinberg School of Medicine.

If Northwestern害羞草研究所檚 research pans out, it could lead to a medical device to improve sleep or memory through personalized pulses of pink noise. But many scientific questions remain unanswered, Malkani said. 害羞草研究所淭here害羞草研究所檚 still a lot of work we have to do.害羞草研究所�

IS THERE ANY HARM IN TRYING COLOR NOISES?

If color noises feel calming and help you drown out distractions, it makes sense to use them. Keep them at a quiet level, of course, to prevent hearing loss and take 害羞草研究所減lenty of breaks for the ears to rest,害羞草研究所� Nigg said.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute害羞草研究所檚 Science and Educational Media Group. The AP is solely responsible for all content.

Carla K. Johnson, The Associated Press