Enter the temperature into the calculator below to determine the speed of sound in dry air.

Speed of sound formula

The following can be used to calculate the speed of sound in air. Note that air is modeled as an ideal gas here. 

 c = √(γ * R * T / M)
  • c is the speed of sound in an ideal gas
  • R is the molar gas constant 8.314,5 J · mol−1 · K−1
  • γ is the adiabatic index 1.4 for air
  • T is the absolute temperature
  • M is the molar mass of the gas. 0.028,964,5 kg/mol (air)

Speed of Sound Definition

The speed of sound is the velocity at which sound travels through a medium. That velocity is dependent on the matter or medium it is traveling through.

In the air, this can be expressed in a simple formula that will be outlined below, but in other mediums, it can be more difficult.

The speed of sound is dependent on the molecules in the medium and how they interact with each other.

This interaction is directly related to the temperature of the material, and so the speed of sound in anything will be faster at a higher temperature.

How to calculate the speed of sound in an ideal gas

The following is a step-by-step guide on how to calculate the speed of sound.

Example Problem:

First, determine the variables that must be known in order to solve the equation.

In this case, the missing variables are y and Y.

Next, determine the values of those variables.

For air, y, known as the adiabatic index, is equal to approximately 1.4. This value is unitless. The temperature or the air is the other variable. For this example, the temperature is assumed to be 10F.

Finally, calculate the speed of sound using the formula above:

c = √(γ * R * T / M)

c = 323.7 m/s.

Analyze the results for accuracy using the calculator above.

FAQ

What is the speed of sound?

The speed of sound is the velocity at which sound travels through any medium.