What this has to do with film is poignant in animation. Animation is a film that the creator controls literally ALL of the aspects of the mise-en-scene. Background, action, sound, lighting it is ALL artificial for an ALL-consuming image. ALL! There, I just wanted to say ALL again. And so it's important to match up sound with image to create an appropriate response. Or vise versa the filmmaker could do opposite association with sound and image to create an inverse test. This has been done in films before as a way to tease the viewer and break down our initial belief of what an object should sound like.
A good example of sound and image coming together as one is found in Tim Burton's first stop motion film "Vincent."
http://www.youtube.com/watch?v=hD8uQzu0IL0
Take a look and maybe you'll get an idea on what should and shouldn't sound like it does!