Sound Inquiry

Engage:

We are in the kingdom of Blam. It's a sad time: the Evil Wizard ___________ has taken all the things from the castle and imprisoned them in small plastic eggs. We can only shake the eggs and imagine what is inside.

Let's shake the eggs and try to determine what's in them.

Explore:

It turns out the Wizard has accidentally left a few things around -- some rubber bands and cups. The royal Good Guys suggest that we may be able to break the spell if we can make music with these items. How many ways can you find to make sounds with just a rubber band and a cup?

Share these ways. Wow, all have MOTION in common.

It looks like the eggs are only responding to the plucked rubber bands. But it's still not music, and the court musicians will need to know how to make music if we are ever going to be able to open the eggs. How can we control the sound?

Share the solutions.

Explain: See Expanded Sound Notes and Activities

Using student data and acting out processes, develop the following ideas:

Sounds are causes by vibrations. The vibrations travel through matter (air, water, etc.) to our ears as compression waves.

Faster vibrations are perceived as a higher pitch. We call use the term frequency to refer to how frequently the vibrations occur. Larger things tend to vibrate less frequently, and smaller things tend to vibrate more frequently.

Harder vibrations are perceived as a louder sound. We call this volume, but it is different that the same term that refers to how much space something takes up. Amplitude is the technical term for how strong the wave is.

Expand:

Someone just found that the Wizard also left some bottles around! Can we make sounds with these? Explore blowing over and hitting bottles with different amounts of water. Notice that the pitch changes with varying levels of water, but that the changes are opposite for hitting and blowing. Why? What must be vibrating in each (water and glass vs. air)?

Evaluate:

1. The royal Good Guys have found a strange instrument that plays different sounds when air goes through it. They have asked you to write a letter to the conductor of the court orchestra (with diagrams) explaining how the instrument might work. (Note: this is the inside of a harmonica. The reeds can be plucked with a fingernail. Also the teacher can show that the sound won't play when the reed is held. Louder sounds come from more forceful breath, pitch changes with the size of the reed.)

Once these letters have been written and collected, the orchestra will play and the eggs will open!

2. Extra Credit. The royal Good Guys also found a video tape labeled "No Air in Outer Space: Star Wars (the accurate sound version)." (Note: the teacher should play a battle scene with the sound off.) What's going on here?