The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
Infrasound is the class of sonic vibrations that are lower than the human ear can hear. That is, they have lower frequencies and longer wavelengths than the sound waves perceived by human beings. The lower boundary on sound perceptible with the human ear is usually around 20 Hertz, or 20 vibrations per second. These waves still travel at the speed of sound (about 330 m/s in air), so their wavelengths can be extremely long.
Infrasound is often produced by large vibrating objects but can also be produced by living things. Elephants, for example, can emit infrasonic waves. Large bridges can be the source of infrasonic pulses when they sway, and nuclear explosions have been known to give off infrasonic waves at frequencies as low as one every hundred seconds (0.01 Hz).
One of the major uses of infrasound in modern science is in the detection of catastrophic storms such as tornadoes. The eye of a tornado generates infrasonic pulses that can be detected from as far away as 100 mi (60 km), allowing for better storm warning systems. While sound, including infrasound, has been studied for many years, new applications are still being explored.