阅读短文，回答问题。 What do you hear? Sounds all

问题：

阅读短文，回答问题。

     What do you hear? Sounds all round you! You can hear the sound of traffic, the wind in the trees, a dog

barking, your own breathing and lots of other things.

    But what is sound? Sound happens when something vibrates (振动) or shakes. We can make something

vibrate by hitting it. Try this experiment (实验). Put your ruler on your desk so that part of it sticks out

(伸出) over the edge. Put your hand on the part of the ruler that is on the desk. Now pull the part that is

sticking out over the edge down, and then let it go.

     The part you let go will vibrate. It will move up and down very quickly, and give out sound. The part

of the ruler sticking out over the edge of the desk produced the sound. If you make that part longer, you

will hear a lower sound. When you shorten it, you will hear a higher sound. Why does this happen?

     When you shorten the ruler, it will vibrate more quickly. When something vibrates more quickly it

produces a higher sound. If you lengthen the ruler, it will vibrate more slowly. When something vibrates

more slowly, it produces a lower sound.

1. How does sound happen?

    ________________________________________________________

2. How can we make something vibrate?

    ________________________________________________________

3. Can we hear a higher sound or a lower sound if we make the part of the ruler sticking out over the edge

    of the desk longer?

   ________________________________________________________

4. What does the word"lengthen" mean in Chinese?

    ________________________________________________________

5. What's the best title of the passage?

   _________________________________________________________