Question Sheet: Earth’s Lowly Rumble


Before reading:

  1. If you were hiking, what natural sounds could you listen for? 
  2. Why might it be useful for animals to hear sounds that people can’t hear?

During reading:

  1. What is infrasound? Where does it come from? 
  2. What makes sounds louder or softer? What are the characteristics of a

    low-pitched sound wave? 

  3. Why did scientists originally start studying infrasound? 
  4. What did scientists learn listening to Sakurajima? Why could what they found

    be important for people’s safety? 

  5. How could elephants use infrasound? 
  6. How might people be able to detect infrasound?

After reading:

  1. What’s the difference between infrasound and ultrasound? See Communications Research Institute). 
  2. How might infrasound help explain why some animals might be able to sense

    danger? See “A Sense of Danger.” 

  3. Why would infrasound detectors be a good way to check whether someone is

    building and testing a nuclear bomb? See


  4. Why might infrasound affect people emotionally? See Angliss, Spacedog). 
  5. Name a possible additional source of infrasound not mentioned in the article. See National Laboratory). 
  6. What kind of equipment would you need to detect and record infrasound? See (Acoustical Society of America).


What is the Comprehensive Test Ban Treaty? When was it signed? What role would a system of infrasound detectors play in helping to make sure the treaty is followed? See (Southern Methodist University).


  1. The Animal Voice Web site, created by the Fauna Communications Research

    Institute, is devoted to communication among animals, particularly at very high

    (ultrasound) and very low (infrasound) frequencies. Visit the institute’s Web

    site at How effective is the Web site? Can you easily find information that you may be looking for? How would you improve the Web site? What would you add? Write one paragraph summarizing what the Fauna Communications Research Institute does. 

  2. Suppose that you are making a documentary film about infrasound. Write a

    description of what you would film for the opening scene of such a documentary.

    What would you show to get the audience interested in the topic? What would the

    narrator say?


Some church organs have pipes that are 20 meters long and produce bass notes at frequencies as low as 8 hertz (cycles per second), which are inaudible to people. If the speed of sound in air is about 340 meters per second, and the speed of a wave is equal to its wavelength times its frequency, what’s the wavelength of 8-hertz infrasound?