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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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