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We’ll be kind–we won’t use any sound effects on today’s program. Instead, imagine your eighth-grade classroom, and your childhood nemesis¹ creeping quietly to the chalkboard. He shapes his hand like a claw, grins evilly, and slowly, torturously², drags his fingernails down the chalkboard.
我们会很友善地对待你-在今天的项目中我们不会使用任何声音效果。只是请想象一下你八年级的课堂，你童年时代的克星静静地站在黑板前。他把手看起来像爪子一样，恶作剧地笑着，然后慢慢地、折磨人地从黑板上划过。

Fingernails
手指甲

Ah, you just winced³, didn’t you? Even without the sound effect. Have you ever wondered why the sound of scraping a chalkboard seems so terrible to the human ear?
啊，你在畏缩，是不是？即使没有声音影响着你。你有没有想过为什么指甲划过黑板的声音听起来如此让人难受？

The Study
研究

A group of scientists from Northwestern University once tried to answer this question. Test subjects were asked to listen to a variety of disturbing sounds and rate them according to their reaction. Not surprisingly, scraping chalkboards with a three-pronged gardening tool rated as the single most disturbing sound. It beat out metal scraping against rusty⁴ metal, styrofoam blocks squeaking⁵ together, and a variety of other sounds.
一群来自西北大学的科学家曾经尝试解答这个问题。实验组的成员被要求去听各种扰人的声音，然后（科学家）根据他们的反应进行评估。不出意外，一个三叉的园艺工具划过黑板的声音被认为是唯一一个最扰人的声音。它击败了金属和铁块摩擦的声音，泡沫塑料块挤压发出的声音，以及很多其他种类的声音。

As it turns out, chalkboard scraping is actually a pretty complicated noise. In addition to the high squeal⁶, there are lower tones as well. Experimenting further, the scientists found that it’s not really the volume or highest squeals⁷ that makes this sound so unpleasant, but the lowest tones that make us cringe.
事实证明，摩擦黑板的声音确实是一个相当复杂的声音。除了高分贝声，也有低音调声。通过进一步实验科学家发现，并非是音量或者高分贝让人感到不愉快，而是最低音让人畏缩。

But why do we cringe at all? There are several interesting theories. For example, the frequency patterns of this sound resemble the warning cries of macaque monkeys. Could our reaction be an evolutionary⁸ holdover, hardwired into our brains? The lower frequencies may also be close to the resonant⁹ frequencies of certain bones in our skulls¹⁰.
但是我们到底为什么畏缩？关于这个有几个有趣的理论。比如，这种声音的频率模式类似猕猴的警告啼声一样。我们的反应会不会是一种进化后的残留反应，这种反应在我们的头脑中驻留下来？这种低频率也许和我们头骨中的特定几块骨头的核磁共振频率接近。

The jury’s still out on this one, so more testing needs to be done. Any volunteers?
在此件事情上，最后结论还待分晓，还需要做更多试验。有人想加入吗？