The speed of sound is the distance traveled per unit time by a sound wave as it propagates through an elastic medium. The speed of sound depends on the properties of the medium, such as the temperature, pressure, and composition. In dry air at 20 °C, the speed of sound is approximately 343 m/s (1,236 km/h or 767 mph). In a gas, the speed of sound increases with the square root of the absolute temperature.