93 Sound-Low

Sound Written by Robert N. Knight

What Is Sound? Do you know what sound is? Do you know how it gets from one place to another? Do you know how you hear sound? Read this book to find out.

A thin layer of air surrounds Earth. Air is made of tiny particles. Sound moves through these particles to get to your ears. Sound is a kind of energy. Like all energy, sound can move things. It can move the particles that make up air. The particles move back and forth and vibrate when there is sound. What makes the particles vibrate?

Let's think about a bat and ball. If you hit a ball with a bat, they will vibrate. This makes the air around them vibrate. The vibrations move away from the bat and ball as sound energy. Wowser! Sound moves very fast. Sound near the ground can travel at 1,200 kilometers per hour (750 mph.) But it moves more slowly high above Earth because there are fewer air particles.

How Do Waves Travel? Sound energy moves through air as a sound wave. In some ways, it is like a water wave moving across water. But sound waves move in all directions. The sound you hear comes to your ears as sound waves.

A sound wave has two parts. One part has air particles packed closely together. The other part has air particles spread out. One part of the wave always follows the other part in a regular way. Different kinds of sounds make waves that look different.