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Speed of Sound in Gas

Speed of Sound in an Ideal Gas


The wave speed of a fluid is equivalent to the speed of sound in the same medium, whether liquid or gas.

The speed of sound is calculated from the Newton-Laplace equation: c=\sqrt{\frac{K}{\rho}} where c = speed of sound, K = bulk modulus or stiffness coefficient, ρ = density.

For an ideal gas, the bulk modulus K = \gamma * P where \gamma (gamma) = adiabatic index or isentropic expansion factor, P = pressure.

The isentropic expansion factor is the ratio of specific heats of a gas at constant pressure and constant volume (i.e. Cp / Cv). For air, this ratio is approximately 1.4 when assumed to be ideal and at 0°C.

Therefore for an ideal gas, the wave speed is given as: c=\sqrt{\gamma * \frac{P}{\rho}}

Speed of Sound in an Ideal Gas Calculator

Calculate speed of sound in gas using isentropic expansion factor (ratio of specific heats):
Formula: c=\sqrt{\gamma * \frac{P}{\rho}}
c = speed of sound
\gamma = isentropic expansion factor (Cp / Cv). (Approx 1.4 for air)
ρ = density
Isentropic expansion factor
Density kg/m³
Pressure Pa
Result: m/s

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