How to make an harmonica

The harmonica was said to be patented in 1821 by Christian Buschmann, a 16-year-old German boy. Since then, it has become the top-selling instrument in the world and a household item in many places. Luckily, creating beautiful noise is not just an art—it is also a science! In this activity, you will design and explore your own harmonica-like instrument made from household items.

Materials

  • Two large craft sticks (at least six inches long)
  • One wide rubber band (#64 size works well)
  • One plastic drinking straw
  • Two small rubber bands
  • A ruler
  • Scissors
  • An adult helper
  • A piece of paper
  • A pen or pencil
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Prep Work

  1. Stretch the wide rubber band over one of the craft sticks lengthwise.
  2. Use your scissors to cut four pieces of straw, each one to one-and-a-half inches long.
  3. Place one of the pieces of straw under the rubber band perpendicular to the craft stick, about two inches from the left side of the craft stick. This is Straw 1.
  4. Place another piece of straw on top of the rubber band to the right of Straw 1. This is Straw 2.
  5. Place the third piece about two inches from the right side of the craft stick, under the rubber band. This is Straw 3.
  6. Place the last piece to the right of Straw 3, on top of the rubber band. This is Straw 4.
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  7. Straws 1 and 4 should be closest to the ends of the craft stick, while Straws 2 and 3 should be in the middle.
  8. With an adult to help you hold the straws in place, put the second craft stick on top of the first one, creating a sandwich with the pieces of straw between the craft sticks.
  9. Secure this sandwich by wrapping a small rubber band approximately a half inch from each end of the sticks. The ends of the sticks should be pinched together with a small space between them created by the straws.
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  10. Use your paper and pencil to draw a table with two columns and five rows. Label the first column “distance between middle straws” and fill in each space below with: “2.5 inches,” “2 inches,” “1.5 inches” and “1 inch.” Label the second column “tone of sound.”

Procedure

  1. To start, move Straws 1 and 4 as close to the ends of the craft stick as possible. You can move the straws by gently sliding them back and forth, but be careful not to pull them out of the sandwich!
  2. Slide Straws 2 and 3 away from each other so that there is a distance of approximately 2.5 inches between them.
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  3. Hold your instrument like a sandwich, with one hand gently holding each end. Try to keep your fingers on the small rubber bands on either side.
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  4. Blow through the opening between the craft sticks as though it is a harmonica (do not blow through the straws!).

    Think about:
    What sound do you hear? Do you feel anything in your hands as you blow through your instrument? Do the craft sticks vibrate or feel different when you play a sound?
  5. Move Straws 2 and 3 closer together, so that there is a distance of 2 inches between them.
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  6. Again, blow through your instrument. Notice the sound and the feeling in your hands.

    Think about:
    Does this sound different than the first time you played it? If so, in what way? Does the vibration of the instrument feel any different?
  7. Again, move Straws 2 and 3 closer together, so that there is a distance of 1.5 inches between them.
  8. Blow through your instrument. Notice the sound and the feeling in your hands.

    Think about:
    Does this sound different than the other times you played it? If so, in what way? Does the vibration of the instrument feel any different?
  9. Finally, move Straws 2 and 3 closer together again, so that there is a distance of 1 inch between them.
  10. Once again, blow through your instrument. Notice the sound and the feeling in your hands.

    Think about:
    Does this sound different than the other times you played it? If so, in what way? Does the vibration of the instrument feel any different?
  11. Return Straws 2 and 3 to their original position, with 2.5 inches between them. Repeat the above steps, this time recording your observations about the tone of the sound in your table. To help you compare the sounds, rate the pitch (highness or lowness) of the sound. Score the lowest pitch sound as a 1, and the highest pitch sound as a 4.
  12. Consider the results in your table.

    Think about:
    Do you notice any patterns in the tone of the sound? Did the tone change as you moved the straws? If so, did moving the straws closer to each other make the tone higher or lower?
  13. Remove all of the straws, except for Straw 1. Try blowing through your instrument.

    Think about:
    Does this sound different than the other times you played it? If so, in what way? Does the vibration of the instrument feel any different?
  14. Try moving the remaining straw and observing how this affects the tone of the sound.

    Think about:
    Can you change the tone of the sound by moving the straw?
  15. Use two other craft sticks, small rubber bands and at least one piece of straw to build a harmonica without the central wide rubber band. You can also disassemble your harmonica and reuse the pieces to perform this test.
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  16. Try blowing through your new instrument.

    Think about:
    Can you make a sound? If so, is the sound different than the other times you played it? Do the craft sticks vibrate or feel different when you blow through it?

What Happened?

The sound made by your instrument is actually the sound created by the large rubber band vibrating as you blow through it, just as a violin string vibrates when played by a violinist. As you blew through your instrument, you might have noticed that you could feel the vibrations through the craft stick. When you rebuilt the instrument without the large rubber band, you probably found that you could not produce any sound when you blew through it. From this you can observe that the large rubber band was essential to creating sound, and that vibrations accompanied the sound.

In addition, you might have noticed that you could change the tone of the sound by moving the straws. When you moved Straws 2 and 3 closer together, the vibrating section of the rubber band got shorter and the tone of the sound got higher. The shorter section of rubber band vibrates more quickly, and our ears pick this up as a higher-pitch sound.

When you removed all but one straw, you probably found that the pitch of the instrument became lower. With only one straw, the vibrating part of the rubber band was probably longer, vibrated slower, and generated a lower-pitch sound. As you moved the remaining straw, you could change the tone as the vibrating part of the rubber band became shorter or longer.

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