<Tr> <Td_colspan="2"> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The speed of sound is the distance travelled per unit time by a sound wave as it propagates through an elastic medium . In dry air at 0 ° C (32 ° F), the speed of sound is 331.2 metres per second (1,087 ft / s; 1,192 km / h; 741 mph; 644 kn). At 20 ° C (68 ° F), the speed of sound is 343 metres per second (1,125 ft / s; 1,235 km / h; 767 mph; 667 kn), or a kilometre in 2.91 s or a mile in 4.69 s . </P> <P> The speed of sound in an ideal gas depends only on its temperature and composition . The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior . </P>

How fast can sound travel in a second