Physics of Sound
Investigation 2
Part 2
Length and Pitch
Students explore four instruments to discover how the length of the vibrating object affects pitch. Students study what happens when the length of the vibrating sound source changes.
3. Lesson set up and Management
Wave Behavior: Describe experiences with sound, for example, vibrations, echoes, and pitch. (PC01 1.1.3)
We can affect pitch by changing the length of the sound source.
Long objects vibrate slowly and have a low pitch. Short objects vibrate quickly and have a higher pitch.
3. Lesson set up and Management
Materials:
This part will take more time for set up. Be sure to have student sheets ready for the waterphone, xylophone, Kalimba, and the string beam. You will need two sets of materials for each instrument. |
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If you place the waterphone bottles in a plastic basin they will be easier to move around the room. |
Set up the Kalimbas and tighten the wing nuts as tight as possible. Tell students they must not change the lengths of the metal strips. The string beams can be a challenge to put together. Be sure to follow the written directions in the teacher’s guide. (The tighter you can get the filament line before adding the binder clip to hold it in place, the better it will work.) |
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Student Management:
You may find this activity the most valuable in the unit as well as the most challenging to manage. One way to ensure success is to set the materials up at each station and model moving from one station to the next exhibiting proper use of the materials at each.
Students often need to be reminded to stay on task at each station. Their attention will need to be directed to their student sheets. Reminding them that they will be participating in scientific investigations may be helpful.
It is very valuable to create time for students to share their observations. Taking time to work as a large group through one student sheet at a time can be very valuable to the students in many ways.
Be sure students strike the waterphone bottles with the wooden mallets BELOW the water line.
Since noise level tends to build during this activity, consider dividing this activity into two separate lessons. Taking a break to reflect on learnings between stations may help.
Spend a few minutes with each miniactivity prior to presenting the lesson so that you feel confident with the materials. This will allow you to focus on student concept and skill development and on classroom management.
Similarities between the tongue depressor and the Kalimba can generate interesting discussions.
You may also wish to discuss similarities and differences between the door fiddle and the string beam.
Understanding the waterphone often requires more time as well as more information. You may wish to discuss the differences in the bottles with more water and those with less and the effect on pitch. Students may have difficulty going between the concepts of more and longer mass and less and shorter mass.
Writing:
Students are beginning to observe specific properties of sound such as pitch and volume. Using a writing prompt that will help you determine whether or not a student understands the difference between pitch and volume will be valuable. You might use the following, “Explain one thing that can change the pitch of an instrument. Use observations from one of today’s activities in your explanation.”