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[科学美国人-60秒科学]（09-04-22）一分钟新闻【已搜索无重复】
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一分钟的科技新闻PDF+mp3，语速中上，有兴趣的可以下一下。五一发一小贴，估计都在放假 http://g.zhubajie.com/urllink.php?id=50177665ve27ync5qzok17i http://g.zhubajie.com/urllink.php?id=50177665ve27ync5qzok17i 下面是全文预览 April 22, 2009 Ear Cells Actively Amplify Sound A study in the journal Public Library of Science ONE reveals that the ear's hair cells act like tiny motors and respond to sound by swaying and driving electrical currents that cause positive feedbacks, which amplify sound. Karen Hopkin reports. Just when you thought you’d heard everything, scientists have found that the reason you can hear everything—including things that are very quiet—is because your ears have tiny tubelike motors that mechanically amplify sounds. You’ve probably heard that it’s the hair cells in your ears that allow you to hear. These cells sport tufts of spiky hairs that are like little molecular mohawks. When sound waves enter the ear these hairs vibrate, and that motion then gets translated into an electrical message that tells your brain that there’s something worth listening to. But the movement of those hairs is not passive, like tall grass swaying in the breeze. The electrical signals they produce feed back on the system, causing the hairs to tilt even more. It’s that so-called “flexo-electric effect” that basically boosts the audio signal and amplifies the sound, findings published in the April 22nd issue of the journal Public Library of Science ONE. The scientists behind the study also note that the length of the hairs in different species explains why animals like bats can detect such high frequency sounds. It doesn’t, however, explain why your kids can hear their cell phone vibrate two rooms away, yet they never seem to hear a word you say. —Karen Hopkin [ Last edited by ltl3s322 on 2009-5-1 at 20:38 ] |
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