Overview

# speed of sound

## Quick Reference

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* = γ*p*, 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* = √(γ*rT*), 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* = *c*_{0}√(1 + *t*/273), where *c*_{0} is the speed of sound in a particular gas at 0°C and *t* is the temperature in °C.

**From:**
speed of sound
in
A Dictionary of Physics »

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Physics