Sound within a game sets the mood, builds tension and educes fear, when a box crashes to the floor you except to hear it and if you don’t it doesn’t seem believable depending on what sound it makes depends on how you ‘read’ what is happening, for example if the box makes a hollow sound then you’ll believe the box is empty but if the sound effects portray that something heavy inside then we will investigate further. Sound makes us believe something is there when maybe it isn’t or it’s hidden.
There are two types of audio within games, sound effects and musical scores. Good sound effects make the game believable whereas good music creates an emotional attachment. Similarly with films if the sound is out of sync or inappropriate then we are less likely to believe it.
There is nothing more irritating than a good game with a terrible sound track. Spyro had possibly the most annoying sound track because it was tacky and repetitive (in hindsight so was the game so it’s fitting in that way.) listening to it now actually offends my ears. http://www.youtube.com/watch?v=YcKr3KKNrZY
For a good sound effects/track they should help shape your emotional response and believability of the game. The music should flow from area to area without noticing the change.