This activity involves building and testing musical instruments.

How do musical instruments work?

• microphone
• Sound Grapher. If you don’t have a Sound Grapher icon on your desktop, go to this link and download the Sound Grapher.
• materials for making musical instruments

This activity addresses NSES standards for physical science (for transfer of energy) and inquiry at grades 5-8
(http://books.nap.edu/readingroom/books/nses/6d.html#ps).

• Do not make loud noises close to other people’s ears. Eardrum damage may result.

1. Make sure your computer has either a plug-in or a built-in microphone. Refer to Technical Hints to connect the microphone.
2. Turn up the input volume for the microphone.
3. Start the Sound Grapher. Refer to this link to download the Sound Grapher. It will open in a separate window.
4. The Sound Grapher shows two graphs. Click on the graph you want to use. Click on the Start button to start the Sound Grapher.
5. As you make noise, wavy lines should appear on the screen. When you click on the Stop button, the graph “freezes” the sound picture at that moment. Here is an example:
   
6. You can then switch to the other graph to look at another sound. The space bar and the Return key also run Start/Stop functions.
7. A single frequency appears as a simple sine wave. When more than one frequency is present in the sound, the waveform is a combination of several sine waves and looks more complex. It is difficult to tell what is happening from the waveform alone, so an additional analysis tool is provided. Click on the “Waves” button, and change the drop-down menu to “Frequencies.” The screen now displays the distribution of frequencies that are present in the sound, with frequency plotted on the x-axis. Here is an example. The first plot shows a sound with five major frequencies; the second sound has two major frequencies.
   

Here are diagrams of several musical instruments. Identify what vibrates to make the sound. How does the player make it vibrate? How does the player control the pitch and the loudness of the sound?

1. Your task is to build a musical instrument and test it using the Sound Grapher. Each group should make a different instrument, in order to make a band with lots of different sounds. Your teacher will supply you with a collection of materials or you can bring things from elsewhere, if you discuss it first with your teacher.
2. The following is a list of goals you should meet with your instrument.
   • It has a sound that lasts long enough so that you can take a snapshot of it with the Sound Grapher.
   • You can change pitch.
   • You can play both soft and loud sounds.
   • You can play a melody (such as “Mary had a little lamb”).
3. If you choose to make drums, they may not meet all of these goals.
4. Make sure your computer has either a plug-in or a built-in microphone. Refer to Technical Hints to connect the microphone.
5. Turn up the input volume for the microphone.
6. Start the Sound Grapher. Use this link to download the Sound Grapher. It will open in a separate window.
7. Record a picture of your instrument’s sound. Keep the picture of the sound by clicking on the Stop button.
8. Using the Sound Grapher, test your instrument and demonstrate that it meets the criteria.
9. Work on the quality of your instrument’s sound. Make it as pleasing as you can. How does this change the appearance of the sound in the “Waves” and “Frequencies” modes of the Sound Grapher?

Demonstrate your instrument to the class and answer the following questions:

1. How do you change the pitch (if you can)?
2. How do you change the loudness?
3. How can you get the sound to last longer?
4. Describe the quality of your instrument’s sound. Quality is hard to put into words, but try it. What does it sound like? (examples: buzzy, tinny, like a bird, like a bell) How does it feel? (Examples might include harsh, clear, fuzzy, soft, sharp, raw, gentle.) How do you change the quality of the sound (if you can)?

In light of your construction efforts, discuss what features are important in a musical instrument. What is required to make an instrument with a beautiful sound?

Bring in and test real musical insturments that you know how to play. Explore how it it tuned, how the frequency and amplitude are controlled, how the sound is amplified by the design of the instrument, and how the sound quality can be changed.