音速是多少公里一小時?

I suppose you refer to the speed of sound in AIR.

The speed of sound in air depends on the air temperature. It can be shown that the sound speed v in air at absolute temperature T is given by the following equation:

v = (20.05).square-root(T) m/s

Thus, at 0'C (= 273 K), the speed of air = 20.05 x square-root(273) m/s
= 331 m/s (= 1192 km/h)

At 27'C (=300 K), the speed of sound in air becomes = 20.02 x square-root(300) m/s
= 347 m/s (= 1249 km/h)

In general, the higher the temperature of air, the faster sound can travel.

音速每小時1236公里

音速約340m/s , 你自己計