Sound being pressure changes

My group choose to do sound for our group project, and since then I was curious on how sounds was made, and particularly how speakers make sound.  Sound is created by areas of increased and decreased pressure in the air.  When created by a speaker they are made by diaphram or center of the speaker moving in and out at rates of a thousand times per second.  AS the diaphram moves outward it creates a wave of increased pressure called condensation, and as the diaphram moves inward it created a wave of decreased pressure called rafefaction.  The thing about this process I found interesting though is that the waves of pressure change the air pressure of the area the air molecules remain mostly unmoved showing that the air pressure changes are predominantly what created sound.  The link shows the power that the waves of pressure have that create sound.   http://www.youtube.com/watch?v=PMg_nd-O688