時尚雙語:你知道iPod對你的聽力影響有多大嗎？

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.

在現在的社會，聽力喪失越來越普遍了。《內科醫學文獻》週一發表的一份調查研究顯示，約16%的美國成年人對日常對話的聽力削弱了，近30%的20週歲以上的年輕人，人數大約在55，000，000，已經喪失了對部分高頻率聲音的聽覺。這項發現重新引起了相關人士及專家的擔心：長時間通過耳機聽大音量的音樂是否會導致人的聽力喪失？來自波士頓兒童醫院的聽力學診斷教授，Brian Fligor解釋了耳機聽音樂的習慣會給你造成多大的影響，以及如何減輕聽力喪失的風險。

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在多大程度上導致了聽力喪失？
??
A：那取決於個人，取決於你每次聽音樂多長時間，以及你在iPod上設置的音量水平。

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.

如果你戴着耳機聽iPod，並且將音量設置在90%或以上，每天大約聽2小時，一個禮拜有五天，天天如此，我們最好的估計是，誰擁有更敏感的耳朵，誰的聽力喪失的程度就更大-以40分貝爲準。這意味着最安靜的時候， 你能聽到40分貝的聲音。這是一種對高聲調的聲音聽力喪失，所以她/他仍可以聽清楚並且明白大多數的日常對話。這種聽力喪失的影響在背景噪音水平上升時表現的最明顯，此時你不得不集中注意力才能聽清楚某人的講話。然後，它開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."

這種情況只會發生在用隨身聽聽音樂10年或者10年以後。我曾經遇到過這樣一個病人，他是建築行業的，當他工作的時候總是戴着耳塞聽音樂，他認爲只要他聽的是音樂聲，而不是電鋸的噪音，就可以保護他的耳朵——因爲他喜歡的是音樂而不是建築施工時的噪音。在28歲的時候，他已經因噪音誘發了50~55分貝的聽力喪失。我們問了一些關鍵性的問題，關於他在與人交流過程中遇到的困難，他給了一個典型的回答，“當我坐在家裏，電視機沒有打開的情況下，我可以很好的明白人們的交談。”他說道，“但是當我去趕赴宴會時，我就會有很大的麻煩。”

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.

這巨大的變化體現了噪音對人的影響有多大，然而，同時這是一個許多研究者正在努力的方向。當然，這裏有很大一部分是屬於遺傳學的。我們得知的多大程度的聲音導致多大程度的聽力喪失，是基於六十年代末和七十年代初，僱主尚未被要求在喧囂的工作環境中保護工人的聽力的情況下的研究。我們發現，當人們長期的暴露在某一特定噪音水平環境中，他們平均都會有一定程度的聽力喪失。但是，人與人之間聽力喪失的程度不同，那些耳朵比較強健的人與耳朵與較柔嫩的人相比，差異可達30分貝。不幸的是，我們直到那些人失去了聽力，也還不知道他們誰的耳朵比較強健，誰的比較柔嫩。那麼，作爲一個臨牀醫師，我必須認真地對待每個人，將他們的耳朵都當做是柔嫩的。

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.

特別對於噪音性聽力喪失而言，耳朵中被損壞的主要區域不是耳膜，也不是你所能看到的耳朵部位，或者中耳內的軟骨，事實上是在耳朵內更深的地方。被損壞的區域是些連接大腦的神經，當然，也包括一些特殊的神經元，聲音信號通過它們進入大腦。我們正在尋找這些內部的毛狀神經元，特別是外部的神經元。當它們長期的使用過度或者刺激過高，它們就會被新陳代謝耗盡。它們工作過度了。它們會臨時性的喪失功能，所以你爲了聽清楚就不得不擴大音量。這些神經元經過一次照射治療後會恢復功能，但是如果你依然像以前一樣讓它們操勞過度，它們最終會死掉，並且你的內耳將會失去那些聽力功能，這些神經元一旦死掉是無法替代的。

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.

根據經驗積累，加上從研究得來的數據顯示，當人們每天用那些標準耳塞聽音樂90分鐘，音量控制在80%以下，能有效的預防和減少患噪音性聽力喪失的風險。但是如果你調的音量越大，那麼持續聽的時間應該儘可能縮短。如果在最大音量的水平，那麼你每天最多隻能聽5分鐘。

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.

我不是特別指iPods。無論哪一種隨身聽都有對人造成聽力喪失的潛在危險。我們已經對MP3播放器進行過研究，並且對於其製造商，我們取得了非常相似的成果。一些內置的耳塞能提供比外掛耳塞更高的音量。這也就是說，我們的行爲研究報告顯示，該類型的耳機與人們設置的不同音量水平幾乎無關。這些設置都取決於他們收聽環境中的背景噪音水平。當我們把人們放在不同的收聽環境中，比如在一架飛行的飛機上——我們利用的噪音是經記錄過的波音757飛機，我們在實驗室內模仿這樣的環境，結果80%的人們最終都設置了那些可能會危害到聽力的音量。在波士頓的鐵路系統中，其環境噪音水平與飛行中的飛機不相上下，雖然它們聽起來不大一樣。這些噪音音量非常高，以至於人們在利用耳塞聽音樂時設置了過高的音量。

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.

我承認我喜歡那種嘈雜的音樂。我非常喜歡在體育館內使用iPod。我想它是一項非常偉大的發明。我甚至鼓勵人們隨心所欲地，想聽多大聲就聽多大聲。但是爲了以你喜歡的音量聽音樂，你必須注意到你聽了多長時間。我還要強烈推薦人們去購買好一點的耳塞，這樣可以屏蔽背景噪音。經過我們研究，發現有的耳塞能完全密封住耳槽。相比那些主動地消除噪音，將噪音排除在外的耳機，這些都是被動的隔音耳機。目前我要說的就是，二者都能讓人們調到自己喜歡的音量——而當人們使用內置耳機時，聲音強度最好調得更低一點。