Suggested uses for this module

• Science - as part of a unit on sound, waves, or physics
• Music - as part of a unit on music or musical instruments
• Art - for a music-oriented craft project, you can emphasize the construction part of the activities, add decorations, and de-emphasize the investigations
• Field Trip - as an introduction or follow-up to a field trip concert or classroom demonstration of instruments.

• Sound Waves - When something vibrates, it makes a sound. The vibrations travel out in all directions from the "something" in the same way that ripples travel out from a pebble that has been dropped in water. But instead of being waves of water, these are waves of vibrations of air: sound waves. Because it is the air itself that is vibrating, sound waves, unlike water waves, are invisible.
• Frequency - or Pitch - Think of water waves again. They can be close together or far apart. If they are close together, there are more of them; they are more frequent. Frequency is the term that scientists and engineers use to describe how many pulses of a sound wave arrive at your ear in one second. Musicians use the term pitch. A sound with a higher frequency (more waves) has a higher pitch, and sounds higher.
• Amplitude - or Dynamic Level - Water waves can also be great, big, tall waves, or small ripples. The size of a wave is called its amplitude. In sound waves, the bigger the wave, the louder the sound is. Musicians call the loudness of a sound its dynamic level.

Materials and Preparation

• Lots and lots of rubber bands, as many different lengths and thicknesses and tightnesses as you can find. If you are using boxes, they must be long enough to stretch around a box.
• Either small, sturdy cardboard boxes, small plastic boxes, OR pieces (about 8" X 10" or so) of thick, flat cardboard, OR square or rectangular baking pans, one for each student or group.
• If you are using flat cardboard, you will also need thumbtacks or pushpins.
• If you are using a box, pencils, pens, or other objects of that size and shape (a couple for each instrument) will be useful.
• You may want scissors that are strong enough to cut the cardboard or plastic.

Procedure

1. Each student or group should choose a variety of rubber bands (3-6, depending on the size of their "instruments")to start with.
2. If you are using flat cardboard, stretch each rubber band between two thumbtacks so that it is tight enough to give a particular pitch.
3. If using a box or baking pan, stretch the rubber bands around the box or pan.
4. Have the students pluck each rubber band separately and listen carefully to the "twang". They are listening for which ones sound higher and which sound lower.
5. To try many different thicknesses and tightnesses, students can trade rubber bands with each other or trade off from the central pile if there is enough.
6. Students with the thumbtack instruments can vary length and tightness by changing the distance between the thumbtacks. Remind the students that when they do this, they are changing both the length and the tightness, so it may be difficult to decide which variable has which effect. Encourage experimentation to see if they can decide.
7. Students with box or pan instruments can vary tightness by pulling on the rubber band at the side of the box while plucking it at the top. Students with lidded box instruments can vary length by slipping a pencil under each end of the rubber bands on the top of the box and then varying the distance between the pencils, or even holding the rubber band down tightly with a finger between the pencils, the same as a real string player does.
8. Students with box instruments can also see if the body of the instrument makes any difference to the sound. Can they play the instrument with the lid off and with it on? Does cutting a hole in the lid change the sound? Does it make it easier to play? Does adding the pencils change the sound or make it easier to play? Do different boxes make a different sound with the same rubber bands? Do cardboard boxes sound different from plastic ones?

Discussion Questions

• Do thicker rubber band "strings" sound higher or lower than thinner ones? (Answer: thicker should sound lower.)
• Do tighter strings sound higher or lower than looser ones? (Tighter should sound higher.)
• Do shorter strings sound higher or lower than longer ones? (Shorter should sound higher.)
• Do there seem to be differences in how loud and soft or how dull or clear a string sounds? If so, what seems to cause those differences?
• Based on their observations, do the students feel they could tell which strings of an instrument were the low strings just by looking at them closely? (For an extra activity, arrange for them to try this with a real instrument.)
• After their experiments, can they explain what happens when a player holds a string down with a finger? What if the same string is held down in a different spot?
• Can the students come up with possible reasons why the thickness, length, and tightness of a string affect its frequency/pitch in the way that they do? (For example, why does a shorter string have a higher frequency/pitch?)(It may help on length to remind them that the longer the waves are, the less frequent they will be.)

Materials and Preparation

• Several narrow-necked bottles, all the same size and shape OR several narrow-necked bottles of varying sizes
• If using bottles of the same size, you will also need water to fill them to varying depths
• If using water, food coloring is very useful to clearly show the depth of the water
• If plastic recorders are available to your students, or a player of a wind instrument is available for a show-and-tell, they can be used for an extra demonstration.

Procedure

1. If using same-size bottles and water, put water in to a different depth in each bottle (for example, an inch in one bottle, two inches in another, three inches in a third and so on). If you have food coloring, and a few drops to the water in each bottle so it is easy to see the depths.
2. Make the air in a bottle vibrate by blowing steadily across the top of the bottle.
3. "Play" each bottle in turn, and arrange them in order from the highest sound to the lowest.
4. If you have the time and inclination, you can even try to "tune" the bottles by adding or pouring out water.
5. If recorders or a wind instrument are available, demonstrate how covering and uncovering the holes on the instrument changes the pitch. Explain that the main vibration in the instrument is happening in the air inside the instrument (just like the air in the bottles), in between the mouthpiece and the first hole that the air can escape from..

Discussion Questions

• If using bottles of different shapes and sizes, how does the size of the bottle affect the pitch/frequency? Does the shape of the bottle seem to affect it?
• Does the size and shape of the bottle seem to affect anything else, like the loudness of the sound or the tone quality?
• What do you think explains these effects?
• If using water in bottles, how does the amount of water affect the pitch/frequency? Why? (You may need to remind the students that it is the air in the bottle that is vibrating; more water means a smaller space for the air; smaller space means shorter waves and higher frequency/pitch).
• If demonstrating with instruments: How does opening and closing the holes of the instruments change the pitch? Why? (Answer: the shorter the distance between the mouthpiece and the first open hole, the shorter the waves and the higher the pitch/frequency. Opening and closing other holes further down the instrument from the first open hole may have no discernible effect - they are not changing the length of the vibrating column of air - or if they are affecting the vibrating air a little, they may change the sound enough to make it more or less in tune.)

Materials and Preparation

• A dowel, rod, or small beam, around 4-6 feet long, held at both ends about five feet off the ground
• Lots of long, thin, objects of different sizes and materials (some suggestions: forks, spoons, spatulas, rulers, windchimes, lengths of chain, legths of pipe or tubing)
• Enough string to hang the objects from the dowel
• Tape if needed to keep the objects on the string
• Something the students can use to strike the objects; a wooden spoon, short stick, pen or pencil, or ruler. Or experiment with different "drumsticks" if you like. Which do the students prefer and why?

Procedure

1. Hang the objects from the dowel with the string and tape.
2. Let the students strike the objects one at a time.

Discussion Questions

• Does the length of the object seem to affect its pitch/frequency? Its loudness?
• Does the material that the object is made out of seem to affect its pitch/frequency? Its loudness?
• Can you tell what effects the thickness of an object has on its sound?
• What seems to affect how long a sound lasts?
• What objects do you like the sound of? Why?
• Which of these effects do you think you can explain in terms of waves and the vibrations the objects must be making?

Materials and Preparation

• Music Box
• Reasonably large, flat surfaces of several different types of materials - different types of wood and metal as well as plastic and softer surfaces will be particularly instructive. Box or drawer made of hardwood optional.
• Large pieces of paper, construction paper, or newspaper OR megaphone
• Tape

Procedure

1. Wind the music box and let everyone listen to it while holding it in your hand.
2. Place the box on different surfaces and listen to the difference it makes in the sound. Continue to wind it as necessary to hear a long example of each surface. If you can, place the music box inside a wooden box or drawer.
3. If you do not have a real megaphone to demonstrate, let the students make their own megaphones by rolling the paper into a cone shape, open at both ends. Tape it if necessary to hold the shape.
4. Let them talk or sing into their megaphones and otherwise experiment with how the megaphone changes sounds. Experiment with different megaphone sizes and shapes (narrow or widely flaring).

Discussion Questions

• What effect does each surface have on the sound from the music box?
• Why?(Answer: when the music box is touching the surface, it starts vibrating, too.)
• Why do instruments have bodies; why aren't they just a bunch of strings or a reed or a membrane to beat on?
• Why would an instrument maker choose to make an instrument body out of wood (like a violin or piano)? Why might metal be chosen (as in brass and many percussion instruments)? Of the other materials you experimanted with, would you make instruments out of them? What kind of instrument with each material? Why?
• How does a megaphone shape change a sound? Does it matter whether the megaphone is narrow or flaring?
• How do you think the megaphones would have changed if they had been made of wood or of metal?
• Would a trumpet sound louder if you were sitting right front of it or behind it?
• Based on your observations, what do you think the shape of the instrument does to the sound of a tuba, trumpet, trombone, clarinet, or saxophone? What about flutes and bassoons (which do not flare)?