The fact that sound needs a material medium for its propagation, an experiment can be performed.
We consider an electric bell inside a closed glass, connected with a vacuum pump. When the glass jar is not vacuumised, the sound reaches to us on the ringing of a bell. But, as the air is taken out from the glass by using a vacuum pump, we will not hear any sound, when there is a perfect vacuum in the jar. This observation confirms the fact that sound requires a material medium to propagate.