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After a three-hour concert by her favorite Norwegian metal band, Anja finds it difficult to hear her friend rave about the show.
在听了她最爱的挪威金属乐队的三小时演唱会后，安雅发现自己听不清朋友对演出的痴迷爆吹。
It sounds like he's speaking from across the room, and it's tough to make out his muted voice over the ringing in her ears.
朋友仿佛是在房间的另一头和她说话，她嗡嗡作响的耳朵很难分辨出朋友喑哑的声音。
By the next morning, the effect has mostly worn off, but Anja still has questions.
第二天早上，这种情况基本消失了，但是安雅依旧心存疑惑。
What caused the symptoms? Is her hearing going to fully recover? And can she still go to concerts without damaging her ears?
是什么导致了昨天的症状？她的听力会完全恢复吗？她可以在不损伤耳朵的情况下继续去现场演唱会吗？
To answer these questions, we first need to understand what sound is and how we hear it.
要回答这些问题，首先我们需要了解什么是声音，以及我们是如何听到声音的。
Like a pebble creating ripples in water, sound is created when displaced molecules vibrate through space.
如同鹅卵石在水中激起涟漪，声音是由位移的分子在空间中振动而产生的。
While sound vibrations can travel through solids and liquids, our ears have evolved to process vibrations in the air.
振动可以通过固体和液体传播，而我们的耳朵已进化到能处理空气中传播的振动。
These waves of air pressure enter our ear canals and bounce off the eardrum.
这些气压波进入我们的耳道，并在鼓膜上反弹。
A trio of bones called the ossicular chain then carries those vibrations into the cochlea, transforming waves of air pressure into waves of cochlear fluid.
三块相互连接的听小骨（名为听小骨链）随之将这些振动传递至耳蜗，将气压波转化为耳蜗液体的振动。
Here, our perception of sound begins to take form. The waves of fluid move the basilar membrane, a tissue lined with tens of thousands of hair cells.
于是我们对听觉的感知开始形成。液体机械波会使耳蜗基底膜移动，这是一个排列了数万毛细胞的组织。
The specific vibration of these hair cells and the stereocilia on top of each one determine the auditory signal our brain perceives.
这些毛细胞的特定振动和每个毛细胞顶部静纤毛的摆动，决定了我们大脑感知的听觉信号。
Unfortunately, these essential cells are also quite vulnerable. There are two properties of sound that can damage these cells.
不幸的是，这些细胞十分重要，但也相当脆弱。两种声音属性能够损害这些细胞。
The first is volume. The louder a sound is, the greater the pressure of its vibrations.
首先是音量。音量越大，振动的压力越大。
While the ear's upper limits vary from person to person,
尽管耳朵能承受的上限因人而异，
close range exposure to sound exceeding 120 decibels can instantly bend or blow out hair cells, resulting in permanent hearing damage.
但近距离接触超过120分贝的声音会立即弯曲或振破毛细胞，从而导致永久性听力损伤。
The pressure of more powerful sounds can even dislocate the ossicular chain or burst an eardrum.
更响声音的压力甚至可以使听骨链脱位，或耳膜破裂。
The other side of this equation is the sound's duration.
另一个属性是声音的持续时间。
While dangerously loud sounds can injure ears almost instantly, hair cells can also be damaged by exposure to lower sound pressure for long periods.
危险的大音量几乎能对耳朵造成瞬时伤害，不过长时间暴露于较低的声压下也会损伤毛细胞。
For example, hearing a hand dryer is safe for the 20 seconds you're using it.
例如，在使用烘手机的20秒内，它的噪音是安全的。
But if you listened for 8 consecutive hours, this relatively low-pressure sound would overwork the stereocilia and swell the hair cell's supporting tissue.
但如果连续听8小时，这个相对较低的声压会过度使用静纤毛并使毛细胞的支持组织肿胀。
Swollen hair cells are unable to vibrate with the appropriate speed and accuracy, making hearing muffled.
肿胀的毛细胞无法以正确的速度和精度振动，令听力变得模糊不清。
This kind of hearing loss is known as a temporary threshold shift, and many people will experience it at least once in their lifetime.
这种听力损失被称为暂时性阈值偏移（即听觉疲劳），很多人一生中至少会经历一次。
In Anja's case, the loud sounds of the concert only took three hours to cause this condition.
在安雅的例子中，演唱会的喧闹只需3小时就能导致这种情况。
Fortunately, it's a temporary ailment that usually resolves as swelling decreases over time.
幸运的是，这是一种暂时的疾病，通常会随着时间推移、肿胀消退而消失。
In most cases, simply avoiding hazardous sounds gives hair cells all they need to recover.
大部分情况下，只需避免危害性的声音就足以让毛细胞恢复。
One temporary threshold shift isn't likely to cause permanent hearing loss.
一次暂时性听阈偏移不太可能会造成永久听力损失。
But frequent exposure to dangerous sound levels can lead to a wide range of hearing disorders,
但是频繁暴露在危险的声音水平会导致各种听力障碍，
such as the constant buzz of tinnitus or difficulty understanding speech in loud environments.
例如持续嗡嗡作响的耳鸣，或在嘈杂的环境中难以分辨他人说话。
Overworked hair cells can also generate dangerous molecules called reactive oxygen species.
过度工作的毛细胞也会产生名为活性氧的危险分子。
These molecules have unpaired electrons, driving them to steal electrons from nearby cells and cause permanent damage to the inner ear.
这些分子携带未配对电子，驱使它们从附近细胞中偷取电子并造成内耳的永久性损伤。
There are numerous strategies you can adopt for preventing hearing loss.
你可以采用很多方式预防听力损失。
Current research around earbud headphone use suggests keeping your volume at 80% or less if you'll be listening for more than 90 minutes throughout the day.
有关耳塞式耳机的最新研究建议，如果一天使用耳机90分钟以上，最好将音量控制于80%以下。
Noise-isolating headphones can also help you listen at lower volumes.
降噪耳机也能帮助你降低音量收听。
Getting a baseline understanding of your hearing is essential to protecting your auditory system.
对你的听力有一个基本的认识对保护听力系统极为重要。
Just like our eyes and teeth, our ears also need annual check-ups.
和眼睛与牙齿一样，我们的耳朵也需要年检。
Not all communities have access to audiologists,
尽管不是所有地方都有听力学家，
but organizations around the world are developing portable hearing tests and easy-to-use apps to bring these vital resources to remote regions.
但是全球相关组织正在研发便携式听力测试以及方便使用的app，将这些重要资源带到偏远地区。
Finally, wear earplugs when you're knowingly exposing yourself to loud sounds for extended periods.
最后，在你知道自己要长时间暴露于大音量声响时，戴上耳塞。
An earplug's effectiveness depends on how well you've inserted it, so be careful to read the instructions.
耳塞的有效性取决于你戴得多好，所以请仔细阅读使用说明。
But when worn correctly, they can ensure you'll be able to hear your favorite band for many nights to come.
不过只要正确地使用，耳塞能确保你在未来的无数夜晚可以继续欣赏你最爱的乐队。
