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Hummers

In this activity, students explore how sound production was used by ancient cultures as a communication tool over long distances.

The bullroarer is an ancient musical instrument used in rituals for communicating over extended distances and in ambushing animals. It consists of a rectangular slat of wood attached to a long cord. As the instrument travels around its circular path, the pitch appears to rise and fall as it moves closer to and farther away from the listener (Doppler Effect). By modifying the cord's length and/or the speed with which it is turned, the sound can be altered. This can be used to code messages over far distances.

Objectives

  • Describe the properties of sound.

Materials

  • a ruler with a hole in one end (per student)
    1m string (per student)

Key Questions

  • Why is this called a hummer? What part of the hummer makes the noise? How could you prove that? Can you vary the sound of the hummer?

What To Do

In class:
Tie a metre-long length of string to the hole in the end of the ruler. 

In a gym or outside:

  1. Space yourself out from your classmates by at least 2 metres.
  2. Twist the string 20–30 times, holding the ruler still. 
  3. As you let go of the ruler, whirl the hummer in a horizontal circle over your head, finding the right speed to make a nice buzzing noise. (Be careful of other students!).

Extensions

  • Play with the length of the string and the speed to produce various sounds. Try using a tool other than a ruler to see if you can make different sounds. Try items like a plastic spoon or a ruler with a postcard taped to it. Brainstorm uses of the bullroarer in ancient cultures. How is a bullroarer similar to our hummer? How is it different?

Other Resources

Science World Resources | Full Unit |  Sound