Exploring the science of sound with kids is both interesting and fun! So what is sound?
Sound is a vibration that grows as an acoustic wave, through a medium like gas, liquid or solid. We interpret these vibrations and waves via our ears and brains. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz can be heard by humans. Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.
Sound waves travel into our ear canals until they reach the eardrum. The eardrum passes the acoustic vibrations through the middle ear bones and into the inner ear. The inner ear is shaped like a tiny snail and called the cochlea. Inside the cochlea, there are thousands of tiny cells that look like little hairs. These cells change the vibrations into electrical signals that are sent into our brains through the hearing nerve. The brain tells you that you are hearing a sound and what that sound is.(source)
With the following fun experiments you can demonstrate sound and experiment with music!
Xylophone Water Glasses
Musical instruments are so much fun to make!
This sound activity shows how different amounts of water in containers change the pitch of the sound created.
4 empty glasses
What to Do:
1. Fill each glass with varying amounts of water.
2. Add a few drops of food coloring to each glass to give it a fun twist.
3. Using the spoon, tap the outside or top of each glass. What sounds are being made? Which glasses have the highest or lowest pitch?
Play around with the water levels in each glass and experiment with pitch! You can even add more glasses and try to create your own songs. Try simple songs like “Twinkle, twinkle little star.”
Listen to Sounds Travel Underwater
Sound travels well through air, but it travels even better through water! This easy sound experiment is best outside on a terrace or balcony, or even perhaps in the bath. The best of course is if you can do it underwater in a pool or a beach.
A bucket filled with water
A large plastic water or soda bottle
At least 2 kitchen knives/spoons
Scissors or sharp knife to cut the bottle
What to Do:
1. After filling the bucket with water, take a sharp knife or kitchen scissors and cut off the bottom of the plastic water bottle. Take the cap is off of the bottle.
2. Instruct your child to place the bottle in the water so that the cut bottom is in the water. Your child will then put his or her ear to the top of the bottle to listen.
3. Using the kitchen knives, clang them together to make a sound, but do this in the bucket of water as your child is listening. What does your child hear?
Your child has probably noticed that the sound of the clanging is loud and clear. Sound travels faster through water than in the air, and animals that live underwater are able to hear sound clearly. Whales and dolphins are well known to make sounds and communicate underwater. In fact you can hear whale sounds several kilometers away.
Whales can also emit low frequency sound waves which we cannot hear. These sound waves can travel very far in water without losing energy. Researchers believe that some of these low frequency sounds can travel more than 16,000 km in some levels of the ocean! Imagine being able to hear noises coming from that far away!
If you go to the beach this summer or are in a pool, try diving under the water and having someone make noise underwater. It’s interesting to use your sense of hearing in this way.
In some spas, they even play relaxing music in the pool water using underwater microphones. You can float with your ears submerged and listen to the music.
Paper Cup Classic
2 paper cups
Long string, like fishing line, kite string
A sharp pencil or needle to poke holes in the cups
What to Do:
1. Start by cutting a long piece of string of at least 10 meters.
2. Poke a small hole at the bottom of each cup.
3. Using each end of the string, thread it through the bottoms of the cups, tying a large knot so that the string does not fall out of the cup. If you make the holes too large, use a washer or paper clip to hold the string in place so that it does not pull out of the cup.
4. Now stand further enough apart so that the string stretches taught between you. Be sure that the string does not touch any other object and that it remains suspended in air as you complete the experiment.
5. Taking turns, talk into the cup, while the other person listens by putting the cup to their ear. Tell your child to repeat what he or she hears after you have spoken and do the same in return!
After the experiment, explain to your child what is happening: sound waves created by talking through the cup travel through the line to the other end, converting back to sound on the opposite side!
Chladni used metal plate covered in sand which he vibrated with a violin bow, and saw how the sand created various patterns depending on the kind of vibration.
Make your own Chladni Vibration Plate!
A bowl or tub
plastic wrap or wax paper
an elastic band or sticky tape
a mini portable bluetooth or wireless speaker
What to Do:
Turn your speaker on and place it inside the bowl. Your bowl needs to be big enough that the speaker sits inside.
Cover the top of the bowl with your plastic wrap or wax paper, making sure that it is taught and stretched evenly across without any wrinkles. Hold it in place with the elastic band or some pieces of sticking tape.
Sprinkle some salt onto the top.
Choose a song with a lot of bass or use the following video to play on the speaker in the bowl.
Watch to see what happens! Your child should be delighted at the way the salt dances on top of the bowl when the bass vibrates the plastic or wax covering.