Friday, January 27, 2012

Sound Explorers: Learning the Science of Sound

Sometimes even birthday presents can lead to home school adventures...

Let's Rock and Roll!

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.



Diagram of the human ear.

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 ear drum 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! 



Dancing Rice

Materials Needed:

1.
Small to Medium Mixing Bowl
2. Heavy plastic (we used a garbage bag)
3. Rubber Band
4. Rice
5. Tape
6. Pot and a wooden spoon (or other large instrument you can beat your drum with)

Instructions:

1. Lay the bowl rim side down on to your large piece of plastic and cut around the bowl making sure to leave extra plastic around the rim (approximately 1 or 2 inches).

2. Secure the bag over the top of your bowl with a rubber band. 

3. Pull the extra plastic down and tape it so that it creates a tight and bouncy surface over the top.

4. Place 1 Tbsp or so of rice grains onto your bouncy surface.

5. Take your pot, with the open side close to the rice, and bang as loud as you can! Watch the rice grains dance and they are pushed by the sound waves coming from your drum!

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

Materials Needed:

1. Several drinking glasses of various sizes
2. Water
3. Metal spoons or forks
4. Food coloring (optional)

Instructions:

1.
Fill your glasses to various levels of water. Make sure you test each glass to ensure that the resulting sound is different. 

2. Add a drop of food coloring to the water and swirl it until it is dissolved. This also provides a quick moment to talk about the different densities in the liquid, as the food coloring immediately drops to the bottom of the glass and takes a while to dissolve on its own. 

3. Hand a spoon to your child and let the symphony begin! I found that putting the glasses on a smooth surface worked best. For us this was the floor, but the kitchen table would have worked just as nicely. 




Note: We did a basic demonstration with water in drinking glasses. There are some interesting methods to this approach that can be found online. One involves making your glasses match an actual musical scale  (C, D, E, F, G, A, B, C.), while another involves using only your fingers to make your glasses "sing"

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

Materials Needed:

1. Plastic cups
2. Yarn
3. Sewing string (optional)
4. Paper Clips (optional)
5. Scissors (pushpins if using sewing string)

Instructions:

1. Cut a length of yarn. Ours was approximately 8 feet long. We cut a smaller length of the sewing string, approximately 6 feet long.

2.Using your scissors, poke a small hole into the bottom of each plastic cup. Make it large enough so that your yarn can go through the hole, but not so big that you can't secure it by tying a knot. If using sewing string, use a thumbtack instead so that your hole is smaller.

3. Feed your yarn through the hole, tying a knot at one end. You'll want the knot to be on the inside of the cups.

4. If you're using the sewing string, tie your knots around a paper clip, so that when you pull the string, the paper clip will stop it from going through the hole. 

5. Pull the cups apart until the string is very tight. This is important, if the string is not taught, the sound waves will not be able to travel along the entire length, and you won't hear anything on the other end. 

6. Start talking!

Experiment!
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!

Materials Needed:

1. Small Box (tissue box, card box, or a small shoe box will work)
2. Rubber Bands (we bought a bag of various sized rubber bands at a CVS for $1.50)
3. Pushpins (3-6)
4. Hot Glue Gun
5. Extra cardboard or paper towel tube for the neck of the guitar
6. Paint, beads, markers, or any other object you can think of to decorate your guitar 

Instructions:

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. 

2. Grab some extra cardboard and measure a neck for your guitar. Kat and I measured out a section approximately 12" long by 2.5" wide. I cut a slit into the top of the guitar and fit the neck inside the slit, securing it with hot glue.

3. Mark off a 3" section in the center of your guitar, both above and below the sound hole. This is where the pushpins will go when you add your strings. 

4. Decorate your guitar! Kat used paint, beads, and some old earring pieces to decorate hers. I asked her to place her beads wherever she wanted them, and I used the hot glue gun to secure them to her guitar. 

5. Stick your pushpins into the guitar. We made a four string, so we put four pushpins in the top, and four in the bottom. 

6. Cut your rubber bands and stretch them until they are tight enough to make an audible sound. Use varying degrees of tightness, and different sizes of rubber bands to achieve different sounds. Tie each end of the rubber band to a pushpin, making sure that your "guitar string" stretches straight across your sound hole.

Safety Note: I found that while the pushpins worked very well in keeping the strings secure, I wasn't as confident about the pushpins themselves staying secure in the guitar. They had already started to pull out with the tension of the rubber band strings. I ended up covering each pushpin with a thick layer of hot glue, and holding them in place until the glue dried. I did one pair at a time (each string), waiting 3-5 minutes each until the glue dried. Once they were all dried, the pushpins didn't budge. Now I'm confident that I won't need to worry about a potential injury if the pushpins pop out. 




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:

Happy Listening!






1 comment:

  1. Good work on this post! I really like the way you delivered your qualitative facts and how you made this fascinating and effortless to realize. Thank you!!

    ReplyDelete