# Learn All About Sound and Sound Waves for Kids

Updated on May 21, 2013

Sound is made by vibrations. Vibrations are back and forth movements. If a door slams, it creates a vibration that moves through the air. When the vibration reaches your ear, you hear it as a sound. These movements of sound through the air are called sound waves. If you throw a stone into water, you'll see ripples form around it. Sound waves are like ripples through the air.

When you speak, your vocal cords create vibrations that move through the air. If you put your hand to your throat and speak, you will actually feel the vibrations from your vocal cords.

## What Is the Speed of Sound?

Sound travels at different speeds depending on the material it must travel through.Sound moves faster through water than it does through air. It travels faster in warm air than in cold air. The speed of sound can be measured in miles or kilometers per hour or in feet or meters per second.

At a temperature of 68 degrees fahrenheit (20 degrees celsius), sound will travel about 770 miles per hour or 1128 feet per second. While that seems fast, it's a lot slower than the speed light travels. Light travels 186,000 miles per second. This is the reason you see lightning before you hear thunder. Both the light and sound are created at the same time but the light reaches your senses before the sound does.

## Breaking the Sound Barrier

At one time, scientists had no idea what would happen to an airplane that traveled faster than the speed of sound. Some thought that a plane would break at such high speeds. On October 14, 1947, scientists finally found the answer.

This was the day pilot Chuck Yeager broke the sound barrier. His plane was called the Bell X-1. This plane couldn't actually take off on it's own. It had to be carried into the air by another plane and then dropped. It was powered by rockets. Yeager fired the rockets to reach supersonic speeds. Supersonic refers to a speed that is greater than the speed of sound. Yeager found that supersonic speed in a plane was actually very smooth.

When a plane breaks the sound barrier, it makes a very loud noise called a sonic boom. When people on the ground watching Yeager's flight heard the sonic boom, they were worried that his plane had exploded.

Airplanes used for passenger travel don't fly fast enough to break the sound barrier. Planes called Concordes were used for commercial transatlantic flights for 27 years. Transatlantic refers to crossing the Atlantic Ocean. Concorde flights were very expensive and are no longer available.

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