樱花电视台:耳朵里的“安全卫士”

一位澳大利亚的研究员认为，咀嚼、谈话或者唱歌可能对保护听力有用。

These simple actions may activate the tiny muscles in your ear to muffle loud sounds, says Dr Andrew Bell from the Research School of Biology at the Australian National University.

安德鲁?贝尔，一位在澳洲国立大学生物研究院工作的博士称，上述这些简单的动作可以激活你耳朵上微小的肌肉，而这些肌肉可以减弱噪音对你耳朵的伤害。

In a paper published in the Journal of Hearing Science, Bell suggests conventional models of hearing don't explain why contracting the muscles of the ear — which some people do voluntarily — can reduce sound by 30 decibels.

贝尔在《听觉科学》杂志上发表过一篇论文，上面写到，人们主动收缩耳部的肌肉，这样就可以降低30分贝的音量，而听力的常规模式并不会解释为什么如此。

The answer, he says, lies in a discarded 19th century theory that suggests the middle ear muscles work like a hydraulic pump.

他说：“你可以在19世纪一条弃置不用的理论那里找到答案，这个理论认为中耳肌肉跟液压泵的作用是一样的。”

This theory may explain why some people seem to have 'tough' ears that are impervious to hearing loss while others are more sensitive, he says.

贝尔称，这个理论可以解释为什么比起其他人，有的人似乎长着 更“结实”的耳朵，他们听力丧失的可能性更小。

"The sound of an opera singer singing can be 100 decibels, so why doesn't an opera singer go deaf?," asks Bell. "The explanation is that when an opera singer sings the middle ear muscles contract."

贝尔问道：“ 歌剧演唱家唱歌的声音都达到100分贝了，但是为什么人家就不会耳聋呢？原因就是，当一个歌剧演唱家唱歌的时候， 中耳肌肉会立刻收缩来保护听力。”

The middle ear consists of three tiny bones — including the smallest bone in the body — two miniature muscles and tendons.

中耳由三块听小骨组成——包括全身最小的骨头——两块极小的肌肉和肌腱。

"If you close your eyes tightly you'll hear a fluttering sound and that's your middle ear muscles at work," says Bell.

贝尔说：“紧闭双眼的时候，你会听到颤动的声音，这说明你的中耳肌肉已经开始“工作”了。”

Under current theories of how the ear muscles work, the muscles and bones of the middle ear stiffen up in reaction to a loud noise, dampening sound waves that travel into the cochlea where fine hairs detect the vibration. 

“从当下关于耳朵肌肉如何工作的理论中，我们了解到，当外部有噪音时，耳蜗处的纤毛感觉到了前庭窗膜的振动，中耳的肌肉和骨头便会立刻变硬来减弱声波对耳蜗的冲击。”

"Obviously [the bones and muscles of the middle ear] have got some sound control function because they're activated when the sound gets loud. 

“显然[中耳的肌肉和骨头]有控制音量的作用，因为随着音量的提高，它们会被激活而开始工作。”

"But that doesn't quite tell you about the fact that when you close your eyes or activate your middle ear muscles you can get a 30 decibel or 1000 times change in the amount of sound that goes through.

“但你不知道，当闭上双眼或者激活你中耳肌肉的时候，中耳肌肉会把你听到的声音音量降低30分贝或者将进入耳道的声波改变1000次来保护你的听力。”

"If you do the model of how that process works in terms of sound conduction, the best you can get is about 100 times. So that doesn't quite seem to be a good explanation of what is going on," he says.

“如果你要做一个声音传导的模型来了解中耳的工作原理，那么你得做大约100次实验才能得到你的答案。因此，那个模型并不能很好的解释中耳肌肉是如何工作的。”

Hydraulic 'pump'

“液压泵”

Instead, the 'pressure theory' proposes the middle ear muscles work like a hydraulic pump, pushing the last bone into the cochlea and increasing the pressure of the watery fluid that fills it. In turn, that pressure squeezes the sensing cells inside and reduces their sensitivity.

“压力理论”认为，中耳肌肉的工作原理跟液压泵很相似，就是镫骨振动时，耳蜗里的前庭窗膜也跟着振动起来，耳蜗内液体的水压升高，并开始流动。水压又反过来压迫耳蜗内部的神经细胞，同时减轻神经细胞的灵敏度。

Bell says better understanding of this mechanism could help prevent hearing loss.

贝尔称，了解这个工作原理能够预防听力丧失。

"We might be able to find ways of making the middle ear muscles more activated. Even if you're chewing or singing along to music you're actually doing something that might encourage middle ear muscle activity that might give you more protection than otherwise," he says.

他说：“我们或许能让中耳肌肉变得更加活跃。即便是咀嚼或者跟着音乐哼唱，比起其它的，我们的中耳肌肉也会因此受到刺激从而更好的保护我们的耳朵。”

It's an issue he says is very important in an age where use of mp3 players is causing hearing loss, but people don't heed the warnings.

贝尔认为在这个人人都听mp3的时代，有个问题至关重要，那就是尽管人们知道常听mp3会导致听力丧失，但是却很少有人理会这些警告。

"Jimi Hendrix sounds awesome when it's loud and people don't want to turn it down.

“当几米?亨德里克斯的音乐声开得很大的时候，它们听起来确实很棒，所以人们不愿意把声音调小。”

"Here we have the middle ear with this natural inbuilt protective mechanism."

“我们该庆幸自己有中耳肌肉，这个内置的保护机构。”

"I think it's worthwhile to open up the question and see what all the options are given that things are going to get steadily worse if we don't do something."

“摊开这个问题并预想可能的后果是如今我们必需去做的一件事，要是我们再不做点什么，后果就会变得越来越糟。”

In the meantime, Bell advocates taking precautions such as limiting exposure to loud music and using over-the-ear ear phones with noise cancellation instead of bud-style ear phones to help prevent hearing loss.

与此同时，贝尔提倡人们采取一些预防措施，比如说，少听重音乐，用头戴式耳机而不是内置耳塞来隔绝外界的噪音，这些都可以预防听力丧失。