The built in Air material, located both in the Built-In and the Liquids and Gases library, is commonly used in applications and models. That material defines common material parameters and their dependency on the ambient pressure pA and temperature T. The relations are simplified and not all thermodynamic dependencies are taken into account. The speed of sound c and the density ρ are defined through the ideal gas law (assuming adiabatic behavior) following

with the ratio of specific heats γ = 1.4 and the specific gas constant Rs = 287 J/(kg·K). This is an idealization of air valid in many cases, see Ref. 5. This means that the speed of sound is not a function of the ambient pressure for this build-in Air material. More detailed relations can of course be entered by defining a user defined material. The dynamic viscosity, the heat capacity at constant pressure, and the coefficient of thermal conduction are all given by polynomial fit curves and only include the dependency on the ambient temperature T.