Continuing our Science for Kids series, Dr. Naomi Lavelle from Dr How’s Science Wows tells us all about sound and how to explain “what is sound?” to your child with 3 fun easy sound experiments for kids to try
What is Sound?
Sound is a type of energy made by vibrations. These sound vibrations move through the air (or other matter) to our ear and our brain can then work out what we are hearing.
Sound vibrations travel as a type of wave that we cannot see. These sound waves need something containing molecules (particles) to travel through. Sound waves can travel through solids, liquids and gases (air), because they are made up of molecules. The molecules carry sound waves by bumping into each other, just like dominoes knocking each other over.
Did you know…sound waves travel in water at a speed of nearly one mile (1.6 km) a second, which is more than four times faster than sound travels through air!
Why do we need two ears?
We need two ears to work out exactly where a noise is coming from; our brain can compare the level of noise reaching each ear and calculate the position of the source of the noise.
Did you know… during the making of the film Jurassic Park, Stephen Spielberg wanted a dramatic effect to signal the arrival of the T. rex.
Inspiration finally came while he was driving home listening to Earth, Wind and Fire and noticed the vibration effect of the base rhythm.
In the film we see ripples in a glass of water, caused by the T. rex‛s footsteps.
This special effect was achieved by someone plucking guitar strings under the dash board!
Can we hear in space?
Sound waves need molecules to travel through so, as there are no molecules in space (or very little) there is no sound in space!!
Did you know… thunder is the sound made by lightning? Sound travels in air at a speed of about one mile in five seconds.
If you count the seconds between seeing the lightning and hearing the thunder you can work out the distance from the source of the thunder!
For example, if you count ten seconds between the lightning and the thunder then you can tell the storm is about two miles away!
What is echolocation?
An echo is made when sound waves you make bounce off a solid object and travel back to your ear. Some mammals use echoes to help to navigate and to find food – this is called echolocation! Bats use echolocation to fly and hunt at night; they send out high pitched squeaks and clicks almost constantly. These sounds are called ultrasonic, they are too high for humans to hear. A bat can tell from the echoes bouncing back to it, where an object is, its size and shape and wheter it is moving or not. Whales and Dolphins use echolocation just like bats, but the ultrasonic sounds they make travel through water instead of air.
Did you know… a bat can detect an object as small as a human hair using echolocation!
3 Fun Sound Experiments to try at home:
#1. Feel Sound Waves!
You will need… a balloon, a radio.
What you do… blow up the balloon and tie it. Turn on the radio to a song with low base music. Hold the balloon between your two hands and hold it very near the speaker of the radio. What can you feel? Change to a different radio station and see if the vibrations change.
So what is happening?… the sound coming from the radio makes the air near it vibrate. The air molecules in the balloon are squeezed more tightly together making them vibrate more strongly. We feel these vibrations in our hands.
#2. Make sound with bottles!
You will need… two identical bottles, water, a spoon.
What you do… fill one of the bottles two thirds full with water and the other bottle one third full. First blow across the top of each of the bottles, which one makes a higher sound? Next tap each of the bottles with the spoon; now which on makes the higher sound?
So what is happening?… blowing across the top of the bottles makes the air inside vibrate. The bottle with less air will make the higher sound.
When you tap the bottles it is the water that vibrates. The bottle with less water will make the higher sound! Small amounts of air or water vibrate more quickly, making a higher sound.
Add some more… if you want to make this even more fun you can use a lot of bottles with different amounts of water and each and see how many different sounds you can get!
#3. Watch sound waves travel!
You will need… a small plastic drinking bottle (empty), a scissors, a small piece of plastic (i.e. a plastic bag), an elastic band, a tea-light, matches.
What to do… use the scissors to carefully cut the end off the plastic bottle (or ask an adult to do it for you). Stretch the piece of plastic over the open end of the bottle and secure it using the elastic band. Ask an adult to light the tea-light for you, and remove the bottle cap. Hold the narrow end of the bottle near the flame and then tap on the plastic at the other end of the bottle. What happens to the flame?
So what is happening?… when you tap the plastic it acts like a drum. The sound waves it creates make the air molecules vibrate. These vibrating molecules then make the molecules beside them vibrate. The vibrations travel through the air in the bottle and blow out the flame.
See demonstrations of experiments here :
Did you try one of the experiments? How did you get on? Tell us in the comments below!