Earth’s Lowly Rumble Additional Information

Recommended Web sites:

Information about the use of infrasound detection to warn of extreme events can be found at (National Oceanic and Atmospheric Administration).

To find out about infrasound from tsunamis, go to (Acoustical Society of America).

You can learn more about elephants and infrasound at (Cornell Lab or Ornithology).

To learn about infrasound and the Sumatran rhino, go to (Acoustical Society of America).

Research on infrasound and cassowaries is described at (American Scientist).

A news report about infrasound “music” is available at (BBC). You can find information about a group that creates infrasonic music at (Sarah Angliss, Spacedog).

Ramsayer, Kate. 2004. Infrasonic symphony. Science News 165(Jan. 10):26-27. Available at

Sohn, Emily. 2005. A sense of danger. Science News for Kids (April 13). Available at

Books recommended by SearchIt!Science:

Exploring Sound— Ed Catherall

Published by Raintree Steck-Vaughn, 1989.

When we use our voices to speak, laugh, cry, and sing, how are we actually making sound? And what happens when that sound reaches your ears? Packed with color photographs and illustrations, this book suggests 15 activities to explore sound for yourself. You’ll discover that a sound is actually a vibration that travels in waves. Find out how sounds can be made softer or louder. Other topics cover deafness, the way echoes work, the speed of sound, and how sound is recorded.

Did You Hear That? Animals with Super Hearing— Caroline Arnold

Published by Charlesbridge Publishing, 2001.

What do porpoises, elephants, bats, and rats have in common? The ability to hear things other animals, including people, cannot. Scientists have learned what animals can hear by “listening” to their behavior. Caroline Arnold explains what they have learned and the methods they used in this vibrantly illustrated book about “super sonic” animals. Mammals, rodents, amphibians, and fish are all represented in the pages of this book. Find out about the amazing world beyond the range of human hearing!

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Power Words

frequency A measure of how often an action or movement is repeated within a certain amount of time. The movement of waves is measured in terms of frequency. The frequency of radio waves is the number of times per second that the waves pass a particular point.

infrasound Sound whose wave frequency is too low (under 20 hertz) to be heard by humans.

wave A motion back and forth or up and down that passes energy from one point to another. Light, sound, and heat travel as waves of energy. In ocean waves, energy passes through the water even though the water molecules do not have any overall forward movement.

Sound, light, x-rays, and other types of energy spread outward in the form of waves. Waves travel through what is known as a medium. A rock dropped in a pool creates waves that travel through the medium of water. Sound waves usually travel through the medium of air.

wavelength The distance between the crest of a wave and the crest that comes before or after it in a series of waves.


Copyright © 2002, 2003 Houghton-Mifflin Company. All rights reserved. Used with permission.

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