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World Sleep Day: Have you heard of brown and pink noise?

The sonic hue universe is quite expansive with pink, blue, violet, and green. Here's an explainer on this ever-expanding world of noise

While sounds of heavy rain is considered brown noise, steady and lighter showers are put under pink noise. (Pixabay)
While sounds of heavy rain is considered brown noise, steady and lighter showers are put under pink noise. (Pixabay)

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For a while now, I reflexively listen to the sound of rain to keep me focused while working. Until this week, I thought it is just ambient music, maybe even white noise but a quick deep dive revealed that it’s brown noise. There’s more. Turns out, the sonic hue universe is quite expansive with pink, blue, purple, and even green. All of them have seemingly different frequencies and are used in varying environments. 

The use of white noise — for newbies it might seem like radio static – has exploded in popularity in recent times with Apple including background sounds on Mac last year. Now, there are varieties of white noise machines, dedicated playlists on Spotify, viral trends on TikTok, and even specifically designed apps. But the question is – does white noise help? A 2020 study published in the journal Noise Health showed that certain noises can enhance environmental comfort and they can improve productivity in a workplace with a healthy environment.

Also read: FutureFantastic: Using tech art and AI to talk about climate action

White noise has also been explored as a therapeutic option for people with attention-deficit/hyperactivity disorder (ADHD). A 2018 study published in Complementary Therapies in Medicine showed that through the phenomenon, of stochastic resonance, white noise could improve symptoms in children with ADHD. Although many use these noises as a way to avoid distractions, there is a lack of clarity regarding scientific evidence regarding their benefits.

Let’s start with understanding some basics about this ever-expanding world of noise. 

Brown noise

You might have heard brown noise without knowing it by its name. The sounds of heavy rainfall, thunder or strong winds that often come with a sense of comfort and calm are put under this umbrella term. ‘Brown noise’ doesn’t refer to the colour but to Robert Brown, a Scottish botanist who discovered Brownian noise in 1827 while looking at pollen grains in water through a microscope. Brown noise refers to low-frequency sound produced by the process that causes Brownian motion. 

Last year, the #brownnoise hashtag reach about 86 million views on TikTok, particularly gaining popularity among the ADHD community, The Washington Post reported. Talking to the daily, one of the users with ADHD said it felt like his “brain was being hugged.” Zadie Smith, the author of White Teeth, also revealed on The Penguin Podcast that she regularly listens to brown noise and that it helped her block out the chaos of New York. Accompanied by it, she says, she can write anywhere.

Although there is not robust research to suggest that brown noise is effective in relieving stress. “Some people think anxiety might be quelled by having a noise blanket to filter out the sounds,” Daniel Berlau, a professor at the Regis University School of Pharmacy told The New York Times.

Pink noise

Pink noise, unlike its better-known cousin white noise, plays the lower frequencies comparatively louder and softer. “Pink noise reduces the high pitches of white noise and becomes a more pleasant sound,” Iris Langman, MSPA, a clinical audiologist at the UW Medicine Northwest Outpatient Medical Center, explains in Right as Rain, UW Medicine's digital publication. “It’s gentle because you are hearing more of the lower frequencies.” 

In a 2010 study, published in the journal Noise Health, light music, an example of pink noise, was beneficial for elder people to improve their sleep quality as a long-term effect. It demonstrated that steady pink noise can significantly reduce brain wave complexity and induce more stable sleep time to improve sleep quality. 

Violet noise

This is seemingly the opposite of brown noise with the volume becoming louder instead of quieter with each octave. This is considered among the higher-pitched noise colours, and some believe it can be useful for treating tinnitus, according to the Sleep Foundation. Although some research suggests sound therapy to suppress tinnitus, a condition that causes sound in the head with no external source, in some people, evidence regarding violet (or purple) noise’s benefits is lacking. 

Blue noise

This is considered high-frequency white noise with each successive octave increasing by three decibels. This results in each octave having as much energy as the two octaves before it combined, according to Live Science. It can sound like a high-pitched hiss. Also called azure noise, the term blue noise is linked to optics, as “the colour blue is on the higher end of the frequency spectrum for visible light.” 

If you are not aversive to high-pitched sounds, blue noise can be good for masking outside noises, according to CNET. Audio engineers often use it for dithering, a process of adding noise to production to smooth out the sound.

Green noise

This one is relatively easy to guess. This is a variation of white noise mixed with nature sounds at a low frequency to induce a calming effect. 

"Green noise is a low-frequency noise at 500 Hertz, and includes sounds from nature such as waves on the beach, flowing rivers, and waterfalls," says Dr Shelby Harris clinical psychologist and behavioural sleep medicine specialist, speaking to Brightly. Green noise can often be found in meditation apps, sound machines, and smart alarm clocks. 

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