Shulou(Shulou.com)11/24 Report--

Think back to the last time you went to a rock concert or fireworks display. Do you remember the strange noise that persisted in your ears after the show? The sound around you briefly disappeared and was replaced by the buzzing in your head, as if your ears were screaming. In a way, they are screaming.

Too much noise can damage the part of our inner ear called hair cells. Hair cells are like goalkeepers for our hearing. When sound waves "hit" hair cells, they convert vibration into electricity, which is transmitted to the brain by our auditory nerves. Without hair cells, sound cannot be transmitted to the brain by "hitting" hair cells, just as sound cannot be echoed in the desert.

Hair cells are located in the shell-shaped cochlea of the inner ear, and above them are bundles of hair-like extensions called static cilia. When sound waves pass through the ear and reach the hair cells, the vibration deflects the static cilia, causing them to move according to the force and tone of the vibration. For example, in static cilia, melodic piano music will make it produce soft movement, while heavy metal will make it produce faster and sharper movement. This movement triggers an electrochemical current that sends information from sound waves to the brain through the auditory nerve.

When you hear a very loud noise, your static cilia will be damaged and constantly send wrong sound messages to auditory nerve cells. In the case of rock concerts and fireworks displays, the hum is heard because the tips of some of your static cilia are actually broken. What you hear is a false buzzing current in your brain, called tinnitus. However, because the body can regrow these tips in about 24 hours, the hum is usually temporary [source: Preuss].

How loud is it? (decibels)

Phone ringtone = 30

Normal conversation = 60

Lawn mower = 90

Chainsaw = 110

Ambulance alarm = 120

Rock concert = 140

12 caliber shotgun = 165

[source: national Institute of Occupational Safety and Health]

How does noise hurt you? You can imagine stuffing the power of an electric guitar solo into something smaller than a marble, and you will see how powerful and fragile our auditory system is. Sound travels in the form of waves and enters our bodies through our ear canal. The tympanic membrane of our outer ear captures waves and vibrates and transmits vibrational information to the bones of the middle ear, where the sound is amplified. The sound waves then move to the inner ear and the pea-sized cochlea, where the hair cells are located. The forces of these vibrations can break the tip of the static cilia and cause a lingering hum, indicating that the noise is too loud.

Repeated exposure to noisy noise can completely kill hair cells. Some people may ask, so what? There are 16000 hair cells in each cochlea of the human body, but that number is negligible compared to the 100 million photoreceptors in the eye, and hair cells act on sound as photoreceptors do on light. Moreover, once these hair cells die, they will not be able to regenerate, which is why it is essential to protect the ear.

How loud is the picture source network? The unit of sound is decibels, which measures the intensity of the sound rather than the quantity. The decibel of a safe sound is often less than 85 decibels. There is a rule of thumb: the probability of shouting someone at arm's length has exceeded the safety threshold of the sound.

Repeated exposure to sounds of more than 85 decibels can lead to very bad consequences. Although tinnitus caused by loud noise is usually short-lived, it happens all the time for people. Chronic tinnitus may be a symptom of infection, high blood pressure and earwax blockage, but it is usually associated with noise-related hearing loss.

There are several simple ways to protect your hearing. First of all, pay attention to the noise level around you. If you know you will be in a noisy environment, such as a rock concert, please wear earplugs. In addition, pay careful attention to how far you are from the noise source and how long you are exposed to the noise, and pay attention to the symptoms of tinnitus. Our bodies are more vulnerable than we think.

White noise and pink noise although excessive noise can cause tinnitus, but there are some noises can help people sleep, this is the "color" noise.

Some people find that pink or brown noise is more conducive to sleep than white noise.

In addition to diet and exercise, sleep is one of the most important aspects of health. Deep sleep is when the body and brain function enters "maintenance mode", which prepares the body and brain for the coming day.

Most doctors would advise people to get at least seven hours of sleep a night, but the quality of sleep is as important as time. Noise pollution from sources such as traffic can cause you to sleep uneasily at night and lack of energy during the day.

Image source: when pixabay cannot solve the noise or shield the source of noise, people may turn to a vertical fan or white noise recorder to help sleep. But white noise is not the only "color" choice. Pink or brown noise may better block out unwanted sounds, which in turn helps you sleep more effectively. Let's take a look at their differences.

White noise and pink or brown noise often wake you up because of the inconsistency of the sound (suddenly from loud to soft, and vice versa), rather than the size of the sound. White noise produces a whole set of sounds to mask the inconsistency of sounds, which spread throughout the spectrum from low frequency to high frequency. They mix together to form a steady stream of "soft" noise. (according to the Sleep Society, "frequency" refers to the speed at which sound vibrates per second. )

The white noise in nature includes drizzle, gentle running water and the sound of a breeze blowing through the trees. People feel very relaxed when they hear these sounds at any time.

Pink noise is similar to white noise, but it tends to be less high-frequency and more towards bass and midrange, so it sounds like moderate rain or waves, and those who don't like high notes may find pink noise more pleasing.

The brown noise further emphasizes the bass notes, almost completely eliminating the high frequency in the spectrum. The brown noise in nature may be roaring rapids, torrential rain and distant rumbling thunder. The noise means Brown noise, which is not only named after color, but also contains the name of British scientist Robert Brown (Robert Brown). In the 19th century, Brown designed a mathematical formula to predict these movements by observing the random movement of pollen particles in water, which is the origin of Brownian motion. When these random formulas are used to generate electronic sound, heavy bass noise is generated because Brownian noise is also known as red noise in contrast to the red light in the visible spectrum.

Which sound is more suitable for sleep? There are still many unsolved mysteries about human sleep patterns in the scientific community, and there are few studies on auditory stimulation and sleep. In 2017, an experiment on eight sleepers at the University of Oxford found that while listening to white noise, the overall sleep time did not change, but the subjects fell asleep faster by 40%. Another 2016 study showed that sixteen young sleepers had a slight improvement in vocabulary memory when they fell asleep under pink noise. Another study by Northwestern University in 2017 (13 older people) linked pink noise to improved deep sleep and memory.

The Iranian Journal of Care Science studied 60 elderly patients with coronary heart disease, half of whom slept in white noise, while the other half slept in the sound of a regular hospital environment. In the control experiment, the scientists found that the sleep quality of people who slept in a hospital environment gradually decreased with the increase of sleep days, while those who fell asleep under white noise remained basically the same throughout the experiment. There are no studies on the effects of brown noise on sleep.

The effects of both pink and brown noise are likely to be subjective before experiments can be conducted with more samples and more diverse participants.

Phyllis Zee, director of the Center for Circadian Rhythm and Sleep Medicine at Northwestern University's Feinberg School of Medicine, said in a CNN article: "I told my patients that I really don't know which kind of noise would be better. Why don't you give it a try and see which makes you more relaxed?"

The effect of mixing these three sounds together is shown in the audio below.

We can get all kinds of noise by getting started with pink noise or brown noise for free or for a fee. It can be found on a variety of media services, including natural and synthetic tracks. There are also dedicated sleep-assisted mobile applications that provide more selective audio options. You can even buy a specially set noise recorder, which is equipped with speakers and a variety of noise options.

Many devices have a timing function, and you can set it to turn off automatically, and then the sound will turn off automatically after you play the sound for an hour when you fall asleep. No matter what the audio source is, adjust the sound to the lowest mode so that the sound is integrated into the surrounding natural environment. Excessive sound can lead to poor sleep quality, so it is recommended to use white, pink or brown noise conservatively.

Interesting things come, in addition to the above color noise, there is also black noise and blue noise. Black noise refers to the absence of noise-silence that is completely silent or occasionally interrupted by sound. Blue noise, in contrast to brown noise, emphasizes high frequency rather than low frequency and sounds like the hiss of a snake. Most people think that blue noise is not good for falling asleep.

Author: Cristen Conger&Talon Homer

Translation: Nuor

Revision: floor-sweeping monk

Original link: Why do loud noises cause your ears to ring? & You Know White Noise, But What's Pink Noise and Brown Noise?

This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop), author: Conger & Homer

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