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Sound through Metal
Name: Lynne
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: 2000-2001
Question:
How fast do sound waves travel through steel?
Replies:
There actually are two different speeds at which sound travels in
steel. Longitudinal vibrations (pressure waves) propagate at around
6000 meters per second; transverse vibrations (shear waves) propagate
at around 3000 m/s. (In air, by the way, only longitudinal vibrations
propagate because air molecules don't hold onto each other tightly
enough to propagate a shear wave.)
Tim Mooney
In solids, there are two kinds of acoustic waves -- longitudinal [the medium
is vibrating in the direction of the acoustic wave] and transverse [the
medium is vibrating at right angles to the direction of propogation]. The
speed of sound is greater for longitudinal waves. The speed of propogation
also depends on the frequency, but for audible sound [~20 cycles/sec. to
~20,000 cycles/sec.] it doesn't change too much. The trend in the speed of
sound is: the harder the material, and the lower the density the faster the
speed of sound:
V(long)(m./sec) V(transv.)(m./sec) density(gm/ml)
Fe(~steel)
5960 3240 7.9
Au
3240 120 19.7
Be
12830 8880 1.87
fused SiO2
5968 3764 2.2
The numbers are from the Handbook of Chemistry and Physics,
publ., Chemical Rubber Co.
V. Calder
The speed of sound in steel is about 5000 m/s (about 16000 ft/s). For
comparison, the speed of sound in DRY air and water are about 340 m/s
and 1500 m/s, respectively. The speed of sound in materials is dependent
on temperature and other factors; the numbers above are for room
temperature.
AK
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