Speed of Sound in Gas – My DataBook

Speed of Sound in an Ideal Gas

Summary
Calculate Speed of Sound in an Ideal Gas

Summary

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