Symbol c or c_s. The speed at which sound waves are propagated through a material medium. In air at 20°C sound travels at 344 m s⁻¹, in water at 20°C it travels at 1461 m s⁻¹, and in steel at 20°C at 5000 m s⁻¹. The speed of sound in a medium depends on the medium’s modulus of elasticity (E) and its density (ρ‎) according to the relationship c=√(E/ρ‎). For longitudinal waves in a narrow solid specimen, E is the Young modulus; for a liquid E is the bulk modulus (see elastic modulus); and for a gas E=γ‎p, where γ‎ is the ratio of the principal specific heat capacities and p is the pressure of the gas. For an ideal gas the relationship takes the form c=√(γ‎rT), where r is the gas constant per unit mass and T is the thermodynamic temperature. This equation shows how the speed of sound in a gas is related to its temperature. This relationship can be written c=c₀√(1+t/273), where c₀ is the speed of sound in a particular gas at 0°C and t is the temperature in °C.