# Speed of sound

distance travelled during a unit of time by a sound wave propagating through an elastic medium

The speed of sound is 1,235 kilometres (767 mi) per hour or 330 metres (1,083 ft) per second in dry air in room temperature. It travels at 1500 meters per second through water. Sound moves faster through liquids and solids than air, since they have a larger specific modulus, meaning they are stiffer. Sound cannot travel through a vacuum, which is a space without any air or matter. The speed of sound is affected by temperature. It travels slower at low temperatures, for example in the stratosphere.

You can calculate the speed of sound like this:

${\displaystyle a={\sqrt {\gamma *R*T}}}$

Where: ${\displaystyle \gamma }$ is the ratio of specific heats (1.4 for air) R is the gas constant (${\displaystyle 287N*m/kg*K}$ for air) T is temperature (in Kelvins)

The speed of sound is also known as Mach 1. Things that go faster are supersonic, and things that go five times that speed (Mach 5) are hypersonic.