Name: Marjorie A.
What are the sources of infrasonic sounds?
Here is a start: Elephants, earthquakes, certain sea dwelling whales, and
large electric power generating windmills.
Infrasound is simply what we call any sound that is below the threshold of
our hearing. Sounds being caused by vibrations, can be produced by anything
that is vibrating at a regular frequency. To be infrasound, we could not
detect it. Scientist for a long time thought that elephants did not
communicate audibly with one another. Some bright guy had an idea to put up
microphones and boost the frequency. It was found that elephants
communicate in this range. As far as any other sources of infrasounds, I am
sure there are plenty. Good luck in your search. The elephants are a
starting point at any rate.
Standing waves in chimneys, wheels of vehicles, vibrations of light poles,
vibrations of trees, trains, very slow rotating equipment
are a few sources that have been measured.
Samuel P. Bowen
Professor of Physics
Department of Chemistry and Physics
Chicago State University
This depends upon several factors. Are you referring to transverse waves
(up and down) or compression waves (back and forth)? The medium through
which the sound waves travels is also an important factor. Do you want a
continuous source, or just a short wave packet? A pipe (like an organ) that
is long enough and wide enough can emit sound waves less than (15-25
cycles/sec) a typical value of the low end cut-off of the human ear. A
piston connected to an appropriate magnet carrying an alternating current of
the appropriate frequency can also work. I'm sure jet engines, or even
propellers produce some low frequency inaudible sound in addition to their
typical "roar", but I do not know what the frequency distribution is.
Click here to return to the Physics Archives
Update: June 2012