From VOA Learning English, this is the Health & Lifestyle report.

You may have heard of white noise being used to cover or hide background sounds. But now white noise has some colorful competition.

There is a growing interest around different kinds of noises. Pink noise, brown noise, and green noise make up a rainbow of calming sounds. And there is a growing interest in their theoretical effects on sleep, concentration, and relaxation.

The science is new. There have only been a few small studies that look at the effects of the noises. But the lack of research has not stopped thousands of people from listening to hours of these noises on YouTube and on meditation apps.

What is pink noise?

Before we look at pink noise, let’s talk about the most common of colored noises — white.

White noise is similar to static on a radio or television. Sound engineers describe it as having equal volume across all the frequencies that humans can hear. It gets its name from white light, which contains all the visible color wavelengths.

However, the high frequencies of white noise can sound severe. Pink noise reduces the sound on those higher frequencies. It sounds lower in pitch, more like the natural sound of rain or the ocean.

Let’s listen to an example of white noise.

[AUDIO EXAMPLE: WHITE NOISE]

And this is an example of pink noise.

[AUDIO EXAMPLE: PINK NOISE]

Brown noise is even lower in pitch. This makes a pleasing sound.

[AUDIO EXAMPLE: BROWN NOISE]

Pink and brown have standard definitions to audio experts. Other colored noises, such as green, are more recent creations. So, their definitions are not as strict.

How are colored noises used to help?

Some research has found that white noise and pink noise may provide help for people with attention-deficit/hyperactivity disorder, or ADHD. These people have difficulty staying on a task or finishing it. This claim comes from a review of limited ADHD studies.

In theory, white and pink noises wake up the brain, said ADHD researcher Joel Nigg. He is with Oregon Health & Science University in Portland.

He is a co-writer of the report “Systematic Review and Meta-Analysis: Do White Noise or Pink Noise Help With Task Performance in Youth With Attention-Deficit/Hyperactivity Disorder or With Elevated Attention Problems?” It appeared in the Journal of the American Academy of Child & Adolescent Psychiatry.

“The noise provides stimulation to the brain without providing information, and so it doesn’t distract,” Nigg said.

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

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

Dr. Roneil Malkani is a professor of brain science at Northwestern University’s Feinberg School of Medicine. He said the frequency characteristics of pink noise are similar to “…brain wave frequencies we see in slow-wave sleep because these are large, slow waves.”

If the research on pink noise at Northwestern University holds up under testing, it could lead to a medical device aimed at improving sleep or memory through pulses of pink noise. These pulses would be made to fit an individual.

But many scientific questions remain unanswered, Malkani said. “There’s still a lot of work we have to do.”

Is there any harm in trying colored noises?

If colored noises feel calming and help you focus, it makes sense to use them. But Nigg offers a few pieces of advice. He suggests keeping them at a quiet level to prevent hearing loss and to take “plenty of breaks for the ears to rest.”

And that’s the Health & Lifestyle report. I’m Anna Matteo.

Carla K. Johnson reported this story for the Associated Press. Anna Matteo adapted it for VOA Learning English.

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Words in This Story

static -n. noise produced in a radio or television receiver by atmospheric or electrical disturbances frequency -n.

wavelength -n. the distance (as from crest to crest) in the line of advance of a wave from any one point to the next corresponding point

pitch -n. the property of a sound and especially a musical tone that is determined by the frequency of the waves producing it : highness or lowness of sound

stimulate -v. to excite to activity or growth or to greater activity : stimulation -n.

distract -v. to draw the attention or mind to something else

pulse -n. an electromagnetic wave or a sound wave lasting only a short length of time