Sometimes even birthday presents can lead to homeschool adventures…
For my birthday this year, my husband bought me an acoustic guitar. I do not yet know how to play the guitar, but I find learning it to be a very fun and rewarding experience. Part of this fun stems from the beautiful sounds that emanate from the strings. Kat and I took turns tightening and loosening the strings as we tuned the guitar, listening to the differences in sound it created. We strummed softly, and pulled hard at the strings, listening to the new sounds we could make. It didn’t take long for these play times to turn into a question and answering session of how sound works. Since I hadn’t thought much about it since elementary school, I figured it was time for a refresher for me, and some fun new demonstrations for her.
We began with a lesson on how the ear works. We learned that the outer ear acts as a collector of sounds. The sound waves travel along the ear canal until they hit the eardrum in the middle ear. The ear drum vibrates against the Malleus (“hammer”), Incus (“anvil”), and Stapes (“stirrup”) Ossicles (the smallest, most delicate bones in your body!), which in turn vibrate against the cochlea in the inner ear. The cochlea is filled with a liquid that sloshes back and forth with the vibrations of the sound waves. This activates tiny cells lined with hairs that send electrical signals to the brain. Finally, those signals are interpreted by the brain as the sounds we hear.
Once we had learned how the ear works, we moved on to sound waves. We knew that sound was caused by vibration, but we didn’t know how you could get different noises out of sound waves. We learned that the speed of vibrations in the sound waves affected the pitch of the noise we heard. If the sound waves were vibrating with a fast speed, the sound would have a high pitch. Slower vibrations resulted in a lower pitch.
Now that we had a basic understanding of how sound works, it was time to do some demonstrations to play with different sounds and test sound mediums. First, we would see if we could demonstrate the effects of sound waves in action!
Small to Medium Mixing Bowl
Heavy plastic (we used a garbage bag)
Pot and a wooden spoon (or another large instrument you can beat your drum with)
1. Lay the bowl rim side down onto your large piece of plastic and cut around the bowl making sure to leave extra plastic around the rim (approximately 1 or 2 inches).
This was a really fun demonstration. Not only could we see an effect from the sound waves, but when we were finished, we were able to use the bowl as a drum! We got two demonstrations of sound for the preparation of one! Now onto the next demonstration. Are there other things we could use in our kitchen to make sound?
Musical Water Chimes
1. Fill your glasses to various levels of water. Make sure you test each glass to ensure that the resulting sound is different.
Okay, so we know that we can observe the effects of vibrations causing sound waves through the air by making rice grains “dance”. We also observed how vibrations can make interesting sounds, and that adding or decreasing the amount of water in each of our drinking glasses can change the pitch of the sound. Now we’ll try to answer another question. Can sound waves travel from one place to another? Specifically, can our ears collect sound waves originating from another room?
A Game of Telephone
We tested both yarn and sewing string to see which material yielded the best results. We were surprised to find that the yarn fared better than the string, even though we thought the “fuzziness” of the yarn would hinder the traveling sound waves. You can also experiment with different materials. You can use tin cans and metal wire instead of string and secure it with a nail. I’ve heard that this is quite effective, although I have yet to try it myself. You can also use fishing line to see if you can hear the sounds with better clarity.
Kat and I sure have learned a lot about sound! We learned that vibrations cause sound, and that those vibrations actually move particles in the air causing the sound waves that reach our ears! Still, there was one final project that we had to do…
Make a Rubber Band Guitar!
Small Box (tissue box, card box, or a small shoe box will work)
Rubber Bands (we bought a bag of various sized rubber bands at a CVS for $1.50)
Hot Glue Gun
Extra cardboard or paper towel tube for the neck of the guitar
Paint, beads, markers, or any other object you can think of to decorate your guitar
1. Cut a sound hole out of your guitar. You’ll want this hole to be relatively smooth, as the smoother your hole is, the better your sound will be. The sound hole serves a purpose to echo (bounce) the sound waves and release them so they can easily reach our ears.
Kat and I had a lot of fun learning about sound and how it works! We also made tambourines and bounced sound off of paper plates. There was one demonstration that we tried and unfortunately, the equipment we had (a $2 thrift store speaker) wasn’t up to the challenge. We’ll try it again next time and hopefully, we’ll get to see this neat demonstration in person! In the meantime, here is a neat video of that fantastic “Oobleck” (cornstarch and water solution) reacting to sound vibrations: