Javascript and audio files

I want to make a website as a learning project to do the following. Plug in a microphone to my computer. Take the audio file and represent it visually as art-- similar to what is done in windows media player skins but I want to do the nuts and bolts and make something my own out of it. I completed my first javascript course and where I am stuck is in my ignorance of how to access the audio data and do my own things with it for fun, like perhaps make a stick figure dance, every time there is an e minor he spins around, something like that. I have a plan once I get a data stream but i don't know how. Any input?