SPEED OF SOUND

The speed of a SOUND WAVE varies greatly when propagated in different media, the PROPAGATION velocity depending on the elasticity (or compressibility), temperature and density of the medium in question.

See also: ACOUSTIC IMPEDANCE, PARTICLE VELOCITY, REFRACTION, SOUND PROPAGATION.

In air, for instance, temperature and atmospheric pressure are significant factors. At 0° Centigrade and 1.013 x 105 Newtons per square meter (normal atmospheric pressure), the speed of sound is 331.5 meters/sec, i.e. 1087 ft/sec or 740 miles/hour. At 20°C (68°F) the speed is 1130 ft/sec or 344 m/sec. Propagation speeds for other media are given in the chart below. For each degree Centigrade increase in temperature, the speed of sound increases by 0.61 m/sec or 2.0 ft/sec.

See: DOPPLER EFFECT, ECHOLOCATION, SONAR, SONIC BOOM, SUBSONIC, SUPERSONIC, SUPERSONIC TRANSPORT, WAVELENGTH.

Speed of Sound in Various Substances

Substance
Temperature (°C)
Speed (m/sec)
Speed (ft/sec)
CO2
0
258
816
CO2
35
274
900
Air
0
331.5
1,087
Air
20
344
1,130
Water Vapor
35
402
1,320
Helium
20
927
3,040
Hydrogen
0
1,270
4,165
Water
15
1,437
4,714
Steel
-
5,000
16,400

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