I just began learning about the topic of sound energy in physics and I already have lots of question that is not being explained with a simple google search. In my research so far, I have learned that in the mechanics of the propagation of sound, it is not the molecules/particles that travel but the energy that is transferred from molecule to molecule. So now with this fact in mind, my question is then that in propagation of sound, why do molecules/particles not travel and keep on traveling in one direction, until its reaches somewhere like the ears of some living being or something. Why does it vibrates, back and forth in stead? Like, what is causing the molecules to move back after it has moved forward where it is carrying the energy of sound?
The reason why I am asking this is that so far from my understanding of sound energy, I tend to conceptualize sound energy as something that originated with some kind of mechanical or contact based force. So like, when I tap/touch on a molecule , that molecule travels a certain distance, which in turn taps/touches another molecule in its path that in turn travels a certain distance, so on and so forth. This situation, in my understanding, is similar to me pushing a macroscopic object like a table by hand, and in this case we know from everyday experience when you push a table, the table as a whole together moves a certain distance. It doesn't travel back and forth. So, thus, unless there is a flaw in my understanding of sound energy so far, my question then becomes that why do molecules/particles in sound energy vibrate in stead of traveling a certain distance? If anyone can add to this question, it will be greatly appreciated. Thank you.