How Bad Are iPods for Your Hearing?

Hearing loss is more common than ever before. About 16% of American adults have an impaired ability to hear speech, and more than 30% of Americans over age 20 — an estimated 55 million people — have lost some high-frequency hearing, according to a new study published Monday in the Archives of Internal Medicine. The finding has got experts — and concerned parents — wondering anew: Does listening to loud music through headphones lead to long-term hearing loss? Brian Fligor, director of diagnostic audiology at Children's Hospital Boston, explains how much damage your headphone habit might cause — and how to mitigate your risk.

在现在的社会，听力丧失越来越普遍了。《内科医学文献》周一发表的一份调查研究显示，约16%的美国成年人对日常对话的听力削弱了，近30%的20周岁以上的年轻人，人数大约在55，000，000，已经丧失了对部分高频率声音的听觉。这项发现重新引起了相关人士及专家的担心：长时间通过耳机听大音量的音乐是否会导致人的听力丧失？来自波士顿儿童医院的听力学诊断教授，Brian Fligor解释了耳机听音乐的习惯会给你造成多大的影响，以及如何减轻听力丧失的风险。

Q: How much hearing loss does an iPod cause?

A: It depends on the person, it depends on how long you're listening, and it depends on the level at which you're setting your iPod.

Q：iPod在多大程度上导致了听力丧失？
??
A：那取决于个人，取决于你每次听音乐多长时间，以及你在iPod上设置的音量水平。

If you're using the earbuds that come with an iPod and you turn the volume up to about 90% of maximum and you listen a total of two hours a day, five days a week, our best estimates are that the people who have more sensitive ears will develop a rather significant degree of hearing loss — on the order of 40 decibels (dB). That means the quietest sounds audible are 40 dB loud. Now, this is high-pitched hearing loss, so a person can still hear sounds and understand most speech. The impact is going to be most clearly noted when the background-noise level goes up, when you have to focus on what someone is saying. Then it can really start to impair your ability to communicate.

如果你戴着耳机听iPod，并且将音量设置在90%或以上，每天大约听2小时，一个礼拜有五天，天天如此，我们最好的估计是，谁拥有更敏感的耳朵，谁的听力丧失的程度就更大-以40分贝为准。这意味着最安静的时候， 你能听到40分贝的声音。这是一种对高声调的声音听力丧失，所以她/他仍可以听清楚并且明白大多数的日常对话。这种听力丧失的影响在背景噪音水平上升时表现的最明显，此时你不得不集中注意力才能听清楚某人的讲话。然后，它开始削弱你的社交能力。

This would happen only after about 10 years or so or even more of listening to a personal audio device. One patient I had used his headphones instead of earplugs when he was on his construction job. He thought as long as he could hear his music over the sound of his saws, he was protecting his ears — because he liked the sound of his music but didn't like the sound of the construction noise. He had a good 50 dB to 55 dB of noise-induced hearing loss at 28 years old. We asked a few pointed questions about when he was having difficulty understanding people, and his response was classic. "When I'm sitting at home with the TV off, I can understand just fine," he said, "but when I go out for dinner, I have trouble."

这种情况只会发生在用随身听听音乐10年或者10年以后。我曾经遇到过这样一个病人，他是建筑行业的，当他工作的时候总是戴着耳塞听音乐，他认为只要他听的是音乐声，而不是电锯的噪音，就可以保护他的耳朵——因为他喜欢的是音乐而不是建筑施工时的噪音。在28岁的时候，他已经因噪音诱发了50~55分贝的听力丧失。我们问了一些关键性的问题，关于他在与人交流过程中遇到的困难，他给了一个典型的回答，“当我坐在家里，电视机没有打开的情况下，我可以很好的明白人们的交谈。”他说道，“但是当我去赶赴宴会时，我就会有很大的麻烦。”

There is huge variation in how people are affected by loud sound, however, and this is an area where a number of researchers are conducting studies. Certainly a huge part of this is underlying genetics. We know how much sound causes how much hearing loss based on studies that were conducted in the late '60s and early '70s, before employers were required to protect workers' hearing in noisy work environments. What was found is that when people are exposed to a certain level of noise every day for a certain duration, they're going to have a certain degree of hearing loss on average. But the amount of hearing loss might differ by as much as 30 dB between people who had the toughest ears and those with the most tender ones — a huge variation. Unfortunately, we don't know who has the tougher ears and who has the tender ones until after they've lost their hearing. So, as a clinician, I have to treat everyone as if they had tender ears.

这巨大的变化体现了噪音对人的影响有多大，然而，同时这是一个许多研究者正在努力的方向。当然，这里有很大一部分是属于遗传学的。我们得知的多大程度的声音导致多大程度的听力丧失，是基于六十年代末和七十年代初，雇主尚未被要求在喧嚣的工作环境中保护工人的听力的情况下的研究。我们发现，当人们长期的暴露在某一特定噪音水平环境中，他们平均都会有一定程度的听力丧失。但是，人与人之间听力丧失的程度不同，那些耳朵比较强健的人与耳朵与较柔嫩的人相比，差异可达30分贝。不幸的是，我们直到那些人失去了听力，也还不知道他们谁的耳朵比较强健，谁的比较柔嫩。那么，作为一个临床医师，我必须认真地对待每个人，将他们的耳朵都当做是柔嫩的。

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Particularly with noise-induced hearing loss, the primary area where the ear is damaged is not the eardrum, not the part of the ear that you can see and not the bones that are inside the middle ear — it is actually deeper inside. It's where the nerve that brings the sound message up to the brain connects with the inner ear, and it involves some very specialized cells. These are hair cells, and specifically we're looking at the outer hair cells. When they're overexposed or stimulated at too high a level for too long a duration, they end up being metabolically exhausted. They are overworked. They temporarily lose their function, so sound has to be made louder in order for you to hear it. These cells can recover after a single exposure, but if you overexpose them often enough, they end up dying, and you lose that functional ability inside your inner ear. The cells that die are not replaceable.

特别对于噪音性听力丧失而言，耳朵中被损坏的主要区域不是耳膜，也不是你所能看到的耳朵部位，或者中耳内的软骨，事实上是在耳朵内更深的地方。被损坏的区域是些连接大脑的神经，当然，也包括一些特殊的神经元，声音信号通过它们进入大脑。我们正在寻找这些内部的毛状神经元，特别是外部的神经元。当它们长期的使用过度或者刺激过高，它们就会被新陈代谢耗尽。它们工作过度了。它们会临时性的丧失功能，所以你为了听清楚就不得不扩大音量。这些神经元经过一次照射治疗后会恢复功能，但是如果你依然像以前一样让它们操劳过度，它们最终会死掉，并且你的内耳将会失去那些听力功能，这些神经元一旦死掉是无法替代的。

As far as a rule of thumb goes, the figures we got in our studies were that people using that standard earbud could listen at about 80% of maximum volume for 90 minutes per day or less without increasing their risk for noise-induced hearing loss. But the louder the volume, the shorter your duration should be. At maximum volume, you should listen for only about 5 minutes a day.

根据经验积累，加上从研究得来的数据显示，当人们每天用那些标准耳塞听音乐90分钟，音量控制在80%以下，能有效的预防和减少患噪音性听力丧失的风险。但是如果你调的音量越大，那么持续听的时间应该尽可能缩短。如果在最大音量的水平，那么你每天最多只能听5分钟。

I don't want to single out iPods. Any personal listening device out there has the potential to be used in a way that will cause hearing loss. We've conducted studies of a few MP3 players and found very similar results across the MP3 manufacturers. Some in-the-ear earphones are capable of providing higher sound levels than some over-the-ear earphones. That said, studies we've done on behavior show that the type of earphones has almost nothing to do with the level at which people set their headphones. It's all dictated by the level of background noise in their listening environment. When we put people in different listening environments, like flying in an airplane — we used noise we'd recorded while flying on a Boeing 757 commercial flight, and we simulated that environment in our lab — 80% of people listened at levels that would eventually put their hearing at risk. On the subway system here in Boston, the ambient noise levels are very comparable to the level on an airplane, although it sounds very different. The noise is sufficiently high that it induces people to listen to their headphones at excessively loud volume.

我不是特别指iPods。无论哪一种随身听都有对人造成听力丧失的潜在危险。我们已经对MP3播放器进行过研究，并且对于其制造商，我们取得了非常相似的成果。一些内置的耳塞能提供比外挂耳塞更高的音量。这也就是说，我们的行为研究报告显示，该类型的耳机与人们设置的不同音量水平几乎无关。这些设置都取决于他们收听环境中的背景噪音水平。当我们把人们放在不同的收听环境中，比如在一架飞行的飞机上——我们利用的噪音是经记录过的波音757飞机，我们在实验室内模仿这样的环境，结果80%的人们最终都设置了那些可能会危害到听力的音量。在波士顿的铁路系统中，其环境噪音水平与飞行中的飞机不相上下，虽然它们听起来不大一样。这些噪音音量非常高，以至于人们在利用耳塞听音乐时设置了过高的音量。

I'm a self-professed loud-music listener. I use my iPod at the gym, and I love it. I think it's one of the greatest inventions ever. I even advocate that people listen to music as loud as they want. But in order to listen as loud as you want, you need to be careful about how long you're listening. I would also strongly recommend that people invest in better earphones that block out background noise. Some of the research we did studied earphones that completely seal up the ear canal. These are passive sound-isolating earphones, as opposed to the ones that are active noise cancelers that block out some of the noise. As far as I can tell, both would allow people to listen to their headphones at their chosen level — and more likely at a lower volume than if they were using the stock earbuds.