Where does sound come from?
Sound comes from any places in a medium such as air where the particles are pushed out of a state of rest through an injection of energy. An easy example is the pressure that comes from speech. Air is forced out of your mouth and the pressure waves are formed (high and low like a wave in the sea) these waves are passed through the air as the air particles are forced together and repel each other, passing the wave along.
It might help to imagine magnets and how when you push 2 of the same sides together they repel, so if you had a long line and you push the first magnet then it would repel into the 3rd and then the 4th etc... till the space is roughly even again.
Now imagine this in every direction from a source such as a stone hitting a floor. Now all these magnets sharply push out and then retract back in. This causes a very sharp pressure wave which we hear as the hit.