Why Can’t We Bear the Sound of Nails on a Blackboard

Most of us can’t bear the sound of nails on a blackboard， but why· Researchers have a possible explanation.

It turns out that our adverse reaction to the piercing sound is partly physical. The part of the noise that makes us suffering has a frequency between 2000 and 4000 hertz， a range naturally amplified by the shape of our ear canals.

And the adverse reaction is partly psychological.

Researchers from Germany exposed participants to the sound of nails on a blackboard as well as similar sounds， such as a fork scraping a plate and plastic squeak.

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 including blood pressure， heart rate and skin conductivity of all persons. All participants were told to rate how pleasant or unpleasant they found each noise to be.

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

The result is that 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.

adverse 不良的

piercing 刺耳的，尖刻的

frequency 頻率

hertz 赫茲

amplify 放大

ear canal 耳道

squeak 吱吱聲

conductivity 導電性

According to the text， if you are told the sound of nails on a blackboard is a kind of music， you will .

A. consider it less unpleasantB. consider it very pleasant

C. hate it as wellD. try to accept it

（Find the KEY in this issue）