Speed of Sound

Depends on the elastic and inertial properties of the particular medium. It also depends on the temperature of the medium. In air, the speed of sound at 20C is 343ms-1.

Gases
In a perfect gas
where
γ = ratio of specific heats
P0 = pressure [Pa]
ρ0 = density [kgm-3]
T = temperature [K]
r = specific gas constant [JK-1kg-1]
The speed of sound is proportional to the square root of the absolute temperature.
where
T0 = 273K
c0 = 331ms-1
T = gas temperature [K]
tc = gas temperature [C]

Liquids
For liquids, the speed of sound is much higher than it is for gases because the density increase for a given pressure increase is much smaller in liquids than in gases. For a pure substance near its critical temperature and pressure, however, the sound speeds of the vapour and liquid phases are not very different.

See also: Approximate Speed, Newtonian Speed of Sound, Sound, Specific Gas Constant.

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Subjects: Audio Noise & Vibration Physics


Weblinks:
NPL: Kaye and Laby The speed and attenuation of sound.