While we’re on the subject of visualizing sound, you may enjoy watching this interesting video :

http://www.youtube.com/watch?v=Q0vgZv_JWfM&feature=related
The artist and experimentor featured here is Norman McLaren, a pinoneer in animation and sound. While you are there, check out some of Mclarens’ animations. They are quite extraordinary considering they were all hand-crafted beginning in the 1930s, before technology made these things somewhat easy.