![]() ![]() ![]() These models are known as “standard atmospheres”. The Earth’s atmosphere is constantly changing, therefore, hypothetical models were developed as an approximation of what may be expected assuming the air does not contain dust or moisture and there is no winds or turbulence. Table - speed of sound in air c, density of air ρ, acoustic impedance Z vs.Definitions, Constants, and Formulas Used in Calculations The below table demonstrates that the properties of air change significantly with temperature. Temperature at altitude h meters above sea level is given by the following formula (only valid inside the troposphere):ĭensity can then be calculated according to a molar form of the original formula: universal gas constant R = 8.31447 J/( mol.temperature lapse rate L = −0.0065 K/ m.Earth-surface gravitational acceleration g = 9.80665 m/s 2.sea level standard temperature T 0 = 288.15 K.sea level standard atmospheric pressure p 0 = 101325 Pa.They are listed below, along with their values according to the International Standard Atmosphere, using the universal gas constant instead of the specific one: To calculate the density of air as a function of altitude, one requires additional parameters. Where p simply notes the absolute pressure in the observed system. p d is found considering partial pressure, resulting in:. ![]()
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