Here is a JAVA game that is supposed to help you visualize how the cooperative motion of individual particles can make up a longitudinal wave.

It is most effective to add the points one by one for quite awhile until the "average" particle motion starts to become apparent. You might want to pay particular attention to how the "loudspeaker" at the end seems to push and pull at the particles and how it is this push and pull that seems to propagate. Also note that every particle is just doing plain old oscillatory motion!