Creating the 'mood of a conversation'

Hey, I'm looking at creating a program me which allows me to show the mood of a conversation visually. Basically I have someone talking into the mic, and when they talk it makes the image on the screen. If you talk loud and fast, the image is bigger and moves faster, where as if you talk quieter the image is smaller and slower. If idea how to do this? I've written up something basic.

Would prefer an email if possible! Thanks!

ethankeating@hotmail.com