“White noise” helps you sleep, is it science or hoax?

Open the video website, enter "noise", and press Enter to see:

"After 300 rounds of fighting with my neighbor about renovation noise, I realized something"

《Anti-noise artifact! A must-have item to make your happiness soar》

…

Annoying noise

(Photo/pixabay)

Just seeing the title, the past scenes of being disturbed by noise began to replay in the little theater in my mind. There were those images, there were those sounds, and a nameless anger surged up.

In addition, the search results seem to contain some fragments of peaceful times:

《Immerse yourself in white noise, meditate and sit quietly》

《White Noise | Orange Cat in Summer, Nap Atmosphere Sound》

…

White noise for a peaceful mind

(Photo/pixabay)

With the sound of the rain falling and the wind rustling through the trees, the irritable mood quickly disappears and the listener can better focus on the present moment.

Why is it that white noise makes people feel relaxed and comfortable, and even a little addicted? As the saying goes, "whiteness hides all ugliness", has the obsession with appearance spread from the visual field to the auditory field?

Hey, wait a minute, how can sound have color?

Since there is white noise, is there also rainbow noise of “red, orange, yellow, green, cyan, blue, and purple”?

It is true, it is colorful and has all kinds of noise.

Part 1

The color of noise

Light is an electromagnetic wave with different wavelengths and frequencies. In the visible light range, low frequencies appear warm, and high frequencies appear cold. In the famous dispersion experiment, sunlight can be decomposed into multiple color bands by a prism, indicating that the white light we usually see is actually a mixture of monochromatic lights of various frequencies (colors).

Dispersion

(Photo/pixabay)

Sound is a mechanical wave, and it also has different wavelengths and frequencies. Noise refers to the sound with irregular and chaotic changes in frequency and intensity within the sound wave frequency band that can be heard by the human ear. Although it changes randomly, it still has statistical characteristic properties and can be distinguished by power spectral density. By analogy with light waves, different noises are named with colors. There are red noise and orange noise whose spectral density decreases with increasing frequency, and blue noise and purple noise whose spectral density increases with increasing frequency. Corresponding to white light, noise with uniformly distributed power spectral density is white noise.

White noise power spectrum

(Photo/Wikipedia)

Of course, absolutely ideal white noise is hard to exist in reality. The sound of rain and streams in nature are only close to white noise or pink noise. The difference between pink noise and white noise lies mainly in the high frequency. The high frequency part of pink noise has lower power. Since the human ear is more sensitive to high frequency sounds, some people prefer "pink" to "pure white".

Part 2

Uses of white noise

Back to the topic at the beginning, why white noise is not annoying, but instead helps listeners stay focused.

Whether it is the whistle on the road or the footsteps coming from upstairs, these noises have certain meanings and will change with the rhythm. The greatest significance of white noise is that it has no special practical meaning and does not distract people. Studies have shown that the brain will resonate with the monotonous and regular sounds of the outside world, and at the same time will cover up other sounds, playing a masking effect. Because there is no change and it does not cause physiological cognition and attention, it will unconsciously weaken the noise that may affect oneself, making it easier to immerse oneself in the current activities.

In addition to studying and working, white noise can be played as background music to improve concentration. In major music software, white noise ranks high on the list of sleep-aid songs. It is believed to have a miraculous effect of relieving late-night emo and improving sleep quality. Sleep-aid products on the market are also generally labeled with white noise.

Part 3

Is it reliable to use white noise to help you sleep?

Using white noise as a non-pharmacological method to improve sleep quality has become a trend nowadays. Is this a scam of capital or a blessing of science?

Let’s take a look at what the researchers have accomplished:

Researchers at the Royal Institute of Medicine in London have studied the effects of white noise on children's sleep. 80% of infants who listened to white noise fell asleep, while only 25% of the control group who did not listen to white noise fell asleep, indicating that white noise has a certain effect on promoting sleep. However, it is worth noting that both data sets only have 20 children.

Researchers at Northwestern University in the United States studied the effects of pink noise on the sleep quality of the elderly. The results showed that the elderly who fell asleep with pink noise were more likely to enter deep sleep and achieved better results in memory testing the next day. It is also worth noting that the data set is only 13 bits.

In order to systematically explore the relationship between white noise and sleep, researchers from the University of Pennsylvania School of Medicine reviewed 38 previous related research papers and came to the following conclusion: white noise can serve as an auxiliary treatment for some neurological diseases and can also block the impact of other noises to a certain extent. However, despite its popularity, the effectiveness of continuous white noise in improving objective and subjective sleep is not clear. Previous results analysis is often based on small sample analysis data sets, and the supporting evidence is not strong enough.

There are also some mouse experiment results that have no direct correlation but are of reference value:

White noise may delay the brain development of young mice, causing the cerebral cortex responsible for hearing and language learning to fail to develop normally. At the same time, long-term exposure to white noise will reduce the brain's sensitivity to auditory space and even damage the brain's comprehensive ability to perceive sound and geographic location.

Poor weak and a little helpless mouse

(Photo/pixabay)

Part 4

Usage suggestions

Whether it is to help you sleep or to isolate noise, you should avoid using white noise for a long time to prevent dependence. Even if you can use magic to defeat magic, white noise is only one way to fight noise. It is more desirable to stay away from noisy environments as much as possible and improve your ability to concentrate.

References:

[1] Riedy SM, Smith MG, Rocha S, et al. Noise as a sleep aid: a systematic review[J]. Sleep Medicine Reviews, 2021, 55: 101385.

[2] Papalambros NA, Santostasi G, Malkani RG, et al. Acoustic enhancement of sleep slow oscillations and concomitant memory improvement in older adults[J]. Frontiers in human neuroscience, 2017: 109.

[3] Spencer JA, Moran DJ, Lee A, et al. White noise and sleep induction[J]. Archives of disease in childhood, 1990, 65(1): 135-137.

Produced by: China Science Expo

Author: He Qi, Hertz Science Press, Institute of Acoustics, Chinese Academy of Sciences

The article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

Please indicate the source of the public account when reprinting

Please indicate the source of the reprint. Reprinting without authorization is prohibited.

For reprint authorization, cooperation, and submission matters, please contact [email protected]