Sound Waves & Making Instruments

Sound Waves & Making Instruments

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Making instruments is a great way to introduce graphs, the concepts of frequencies, and sound physics!

Overview

Making your own instruments is another fantastic activity that is approachable by students of all ages, both reinforcing and introducing mathematical concepts of varying levels. This activity also encourages freeform play that allow students to challenge themselves with "what if?" questions and explore for their own interest in learning!

Materials

The materials you need for this activity can be just about anything you want, but here are some of our recommendations to get started!:

  • Straws (different colored packs are the best way to go!)
  • Paper towel/toilet paper rolls
  • Recyclable produce and sandwich containers
  • Masking and/or Scotch tape
  • Rice, beans, or Bbads, or other similar material
  • Rubber bands
  • Paper
  • Crayons, markers, etc. for decorating!

Project Background

Did you know that sounds can be described mathematically? We can draw graphs that represent the volume (how loud or quiet a sound is) and the pitch (how high or low the sound is). More importantly, when we understand the pattern of these sounds, we know how to achieve these desired sounds when making instruments.

Here are two examples of sound waves:

What do we notice about these waves? The louder ones are taller compared to the soft waves. That is, they have a higher amplitude (height of the wave). The higher the amplitude of a sound wave is, the louder it is.

However, we also notice that both sets of these waves have cycles that are about the same width. (A cycle is equal to a single wavelength, which is the distance from one point on one single wave to the same point on the next adjacent wave.)

So what happens if we change the width of a wave cycle?

The skinnier the waves get, the more of them we can fit together in the same amount of time. This is higher frequency: the waves cycle more frequently in a given time frame. A higher frequency means that our ears hear a higher pitch, like a whistle. A lower frequency means that we hear a lower sound, like a bass drum.

How quickly an object vibrates determines the pitch that our ears hear. Think of a guitar, which has 6 strings, all different sizes. Imagine that you pluck the skinniest string, and you watch it vibrate as it plays a high note. Then you pluck the thickest string, which plays a much lower note. Why is that? Because the thickest string is just that - it's thicker, meaning there's more material to it (more mass); it cannot vibrate as fast as the skinniest string.

The frequency we hear from many types of instruments depends on how long or how thick parts of the instruments are. So how can we use this knowledge to create musical instruments?

 

Making a Shaker

Create a very simple shaker!:

1. Grab a yogurt cup and a lid. If you don't have a fitting lid, create a cover with cardboard.

2. Fill the yogurt cup about halfway with rice.

3. Close up the shaker by taping on a lid or other cover.

4. Decorate!

5. Now, create a second shaker by changing one variable of your original design:

  • change the size of the yogurt cup,
  • the amount of rice you put in,
  • or the material itself that you put inside the cup (such as using beans or beads instead of rice).

Once you've closed up your second shaker, give it a try. How does it sound compared to your first shaker? Is it a higher pitch or a lower pitch? Why do you think?

 

Making a Drum

1. Start with a closed container of any kind: a shoebox, a produce container, or tupperware from your favorite thai take-out!

2. Grab a couple of wide, flat lids - something big enough you can drum on!  Lids from containers such as sour cream or cottage cheese are good examples.

3. Tape or glue the lids onto the closed container.

4. Create another drum of a different size - how does the sound compare to your first drum?

5. Create a third drum, but this time, fill the container with crumpled construction paper or something similar. How do the sounds compare now? What if you filled your drum with something like beans or rice? What kind of sound effects might you get when you play your drum?

Making a Pan Flute

1. Start with a collection of straws that are all the same width. Ideally, grab a straw of every color!

2. Cut each straw the following lengths for their corresponding notes:

21 cm Do
18 1/2 cm Re
17 cm Mi
16 cm Fa
13 1/2 cm Sol
12 1/2 cm La
11 cm Ti
10 1/2 cm Do

3. Tape all of the straws together from tallest to shortest, lining up one side of each straw's end to create a flat top to your flute.

4. Decorate, play, and enjoy!

For younger artists, cutting straws in any different lengths is just as effective for exploring how different length straws make different sounds.

Making a Guitar

1. Start with a shoebox, tissue box, strawberry container, or similar rectangular prism item. You will need the box to have some kind of opening: you can either leave the lid off of the shoebox, or cut a hole in the lid. 

2. Select at least four different rubber bands to stretch over the container. Choose bands that have different lengths or different widths. Try to select rubber bands that are only different by one variable.

3. Place the rubber bands over the open container, spaced apart equally.

4. Take a paper towel or toilet paper roll and tape one end of it to one of the smaller sides of your rectangular container. This creates the "neck" of the guitar - just for aesthetic purposes!

5. Decorate!

6. Try strumming some of the different bands on your guitar. Which one makes the deepest sound? Which one makes the highest sound? How do the lengths and widths of these rubber bands compare? 

Looking at the lengths and widths of each of your rubber bands: can you try placing them in order on your guitar so that your strings play in order from lowest to highest?

Discussion Questions

Our brains better retain information when we engage both our hands and minds in the activity. Now that we've explained how to engage the hand, what are some discussion questions to engage the mind during the activity?

1. Why does the longer pipe of the pan flute make a lower sound than the shorter pipe of the pan flute?

2. Why does the skinnier rubber band make a higher sound than the fatter rubber band?

3. If we made two shakers where one shaker had a lot more rice than the other shaker, how do you think the sounds of the shakers compare? Why?

4. If we made one shaker with rice and the other with beans, how do you think the sounds of the shakers compare? Why?

Supporting Resources

Explore the oscillations (wave patterns) of the sounds your instruments make by visiting this Virtual Oscilloscope and playing your instruments in front of your computer's microphone!

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