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Sound velocity definition and calculation for an ideal gas


Section summary
1. Definition of the sound velocity
2. How to calculate the sound velocity
3. References of speed of sound in air
4. Excel calculation tool for sound velocity

1. Definition of the sound velocity in an ideal gas

The sound velocity, sometimes also called the speed of sound, is the distance traveled by a sound wave in a gas during a unit of time. It is generally expressed in m/s and is used in many process engineering calculations.


2. How to calculate the sound velocity for an ideal gas

The following formula can be used to calculate the speed of sound in an ideal gas :

Speed of sound formula for ideal gas

With :

a = speed of sound in m/s
k = specific heat ratio or isentropic coefficient
R = perfect gas constant = 8314
T = gas temperature in K
M = molecular weight in g/mol

3. References of speed of sound for common fluids

Gas
Speed of sound in m/s
Air 20c 343 m/s
Air 100c 386 m/s
Air 150c 410 m/s



4. Excel Calculation Tool

The following Excel calculation tool will allow you to calculate the sound velocity for ideal gas : link to Excel calculation tool