I know that on an engine the energy of the fuel is converted in heat, power and noise. I know htat an explosion makes caboom because of the huge air dislocation. But why does the floor make noise when we walk? Is it only because of the vibration of air caused by its movement…? Yes, this is a stupid question 
They vibrate, emitting vibrations into the adjacent air, some of which are recognizable to the human ear within what we call “audible range”.
Yep.