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Speaking Involves Air, Vibration and Muscle

What is involved when we make a sound with our vocal cords? Students explore the mechanics of vocal cords in this activity.

You can feel that speaking involves vibration. Vocal cords are stretchy flaps of skin in your throat that vibrate to make a sound. In order to speak, we move air past our vocal cords, which makes them vibrate. The vocal cords must be in good shape for speech to sound clear and loud. Air being let out of a balloon mimics how air passes through the vocal cords to produce sound.

We change the sounds we make by stretching and contracting the muscles attached to our vocal cords. The sounds found in the word "gllloooooooo" stretch the vocal cords in different ways. When the vocal cords are stretched out we make high sounds and when they are loose we make lower sounds. A great video of vocal cords in action (courtesy of the filming of a laryngoscopy procedure) can be found at Auditory Neuroscience.

Adjusting the tension in the opening of a balloon as the air comes out demonstrates how to vary pitch. As air is forced out of a balloon or whoopee cushion's narrow opening, it makes the rubber vibrate. This in turn makes the air surrounding the rubber vibrate, propagating waves through the air to your ears, translating into sound. When blowing through their "fart whistles," students get to both see and feel the vibrations of the sound.

When you speak, you use the muscles in your tongue, lips, jaw, and pharynx to make the vocal cord vibrations into words. Adjusting the neck and "mouth" of the balloon mimics how human voices are changed by the actions of their anatomy.

Objectives

  • Describe how sound is produced.

Materials

  • Per Class:
    balloons (1 for each student)
    a chair
    10–15 pairs of scissors
    whoopee cushion (for optional activity in Part 3)

Key Questions

  • Part 1
    • When we are talking to each other, which parts of our bodies form the sounds and words we use?
    • What causes the vocal cords to vibrate?
  • Part 2
    • What would we sound like if we could not change the pitch of our voices?
    • What part of the demonstration represents the muscles involved in speech?
    • What part of the demonstration represents the vocal cords?
    • What part of the demonstration represents the lungs?
  • Part 3
    • What makes the silly sound?
    • Can you modify your fart whistle to make a different sound?

What To Do

Part 1: Speaking involves vibration

  1. Get the class to put their fingers on their throats and say “GLLLLOOOOOOO” to feel their vocal cords vibrate.

Part 2: Speaking involves air and muscles

  1. Blow up a balloon and make sounds by letting the air out.
  2. Stretch the neck of the balloon to make a high sound and slacken it to make a low sound. This represents the stretching of the vocal cords to vary pitch.
  3. Hand out the balloons to the students.
  4. Challenge them to produce various pitches with their balloons.
  5. Repeat Part 1 several times, adjusting the pitch (higher, lower) and volume (louder, softer). Now try it without making your vocal cords move.

Teacher Tip: This part also works well as a classroom demonstration.

Part 3: A fun application of air, vibration and muscles: the fart whistle!

  1. Choose a volunteer to sit on a chair facing the students.
  2. Ask them to stand up then sit down, and repeat several times.
  3. Sneak a whoopee cushion onto their chair at some point, just before they sit down!
  4. To make a whoopee cushion-like “fart whistle”, the students cut off the top of their balloon (about midway of the round section).
  5. The students blow through the neck of their balloons to mimic a farting sound.

Teacher Tip: Tell students not to use the balloons in front of other students’ faces, as the fart whistles will spray spittle everywhere.

Extensions

  • Try taking in a long breath and speak at the same time. How does it affect your speech? (For functional speech to occur, air must be going out, not coming in.)
  • If you get your mouth “frozen” at the dentist’s office, what happens to your speech? Why?
  • Do an interpretive dance of how pitch is controlled. Include the actions of the lungs, the air, the vocal cords, and the muscles that control them.