我们为什么受不了指甲刮黑板的声音？

Most of us can't bear the sound of nails on a chalkboard , but now, researchers have a possible explanation as to why the sound makes us cringe and cover our ears.

我们大部分人都忍受不了用指甲刮黑板的声音，现在科学家们对我们无法忍受这种声音并忍不住要捂耳朵的现象有了一种解释。

It turns out our adverse reaction to the piercing sound is partly physical and partly psychological, and that the part of the noise that makes us wince has a frequency between 2,000 and 4,000 Hz (hertz), a range naturally amplified by the shape of our ear canals, Wired Science explains.

我们对刺耳的声音做出的不良反应一部分是生理的，一部分是心理的。这种让我们难受的声音一般是在2000-4000赫兹之间，由于我们耳廓的形状，这个区间内的声音会被放大，Wired Science解释说。

Researchers from the Macromedia University for Media and Communication in Germany and the University of Vienna worked together to get to the bottom of the sound's bad rep.

来自德国Macromedia传媒学院和维也纳大学的研究者一起研究出了出现这种情况的原因。

They exposed participants to the sound of nails on a chalkboard as well as similar sounds, such as a fork scraping a plate and Styrofoam squeak, according to ScienceNow.

ScienceNow刊文显示，科学家们揭示了测试参加者无法忍受类似于指甲刮黑板、叉子刮盘子和塑料摩擦的声音的原因。

Some were told the sound was part of a "musical composition," while others were told the source of the noise. The researchers measured the physical reactions (blood pressure, heart rate, skin conductivity) of all persons. All participants were told to rate how pleasant or unpleasant they found each noise to be.

科学家们告诉一部分受测试者，说这是某个“乐曲”的一部分，而告诉另一部分受测试者，说这是噪音。通过测量受测试者的身体反应(包括血压、心率、皮肤传导性)，来得知受测试者对这段音乐的反应。

Researchers also experimented with removing certain parts of the sound in an effort to identify which parts participants found unpleasant.

研究者试着移除整段声音的某些段落，试图找出是哪一段让人有不舒服的感觉。

If people knew what caused the noise, they tended to rate it as more unpleasant. Those who were told the noise was part of a tune rated it as less unpleasant. However, both groups had measurable physical reactions to the displeasing frequencies, despite how they rated the sound, Wired Science points out.

如果人们知道造成这种噪声的是什么，觉得难受的几率会增加。而被告知这是乐音的人，觉得难以忍受的几率则会较低。Wired Science指出，不论他们怎么看待这段声音，两组受测试者对这种让人难受的音频频率都表现出了一定的身体反应。