Lesson 16
Sound and Vibrations
Learners begin their exploration of sound by discovering its most fundamental truth: every sound in the universe starts with vibration. Through a series of hands-on demonstrations (plucking a rubber band near the ear, humming and feeling the throat, and watching a tuning fork in slow motion) students build direct physical evidence that sound and vibration are inseparable. The lesson puts that principle to work with a hands-on build: students construct a popsicle stick harmonica and use it to explore how changing the vibration changes both pitch, through frequency, and loudness, through amplitude.


Key Ideas
  • All sound begins with vibration — rapid back-and-forth movement of an object.
  • When vibration stops, sound stops. The two are inseparable.
  • Frequency is the number of vibrations per second. Higher frequency produces higher pitch; lower frequency produces lower pitch.
  • Amplitude is how far the vibrating object moves. Larger amplitude produces louder sound; smaller amplitude produces softer sound.
  • Pitch and loudness are independent of each other. A sound can be high-pitched and quiet, or low-pitched and very loud.
Vocabulary
  • Vibration: Rapid back-and-forth motion — the source of all sound.
  • Frequency: The number of vibrations per second. Determines the pitch of a sound.
  • Amplitude: How far the vibrating object moves. Determines the loudness of a sound.
  • Pitch: How high or low a sound is, determined by its frequency.

Hands-On Activity: Build a Popsicle Stick Harmonica
Supply List
  • 2 jumbo popsicle sticks
  • 1 large rubber band
  • 2 small rubber bands
  • 1 plastic straw
  • Scissors
Instructions
  • Stretch the large rubber band lengthwise around one popsicle stick so it runs the full length of the stick.
  • Cut a piece of straw about 1 inch long. Slide it under the rubber band near one end of the stick.
  • Place the second popsicle stick on top. Wrap a small rubber band tightly around that end to hold both sticks together.
  • Cut a second 1-inch piece of straw and slide it between the sticks at the other end.
  • Wrap the second small rubber band tightly around that end. Your harmonica is ready.
  • Place your lips over the large rubber band in the middle and blow gently to play.
Experiments: Move the straws closer together and blow again — notice how the pitch rises. Then keep the straws in place and blow hard, then soft — notice that the pitch stays the same while the loudness changes.

Supplies for Live Class (same for the experiment)
  • Rubber Bands 
    • 1 larger flat rubber band 
    • 2 Smaller 
    • Various other sizes
  • Two JUMBO popsicle sticks (the wider ones)
  • Plastic Straw + Scissors to Cut it
  • OPTIONAL: Stringed instrument, xylophone, bell, or tone-making item. Tuning fork is especially useful, but not required.

Sources
C-2 Sound by Selene
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