how to modify "speak here" to get audio level meter?

Hi After reading so much on the speak here apple's example, i couldnt understand what parts of it i need .

I only need to always get the audio data from mic , and check the power of it , in order to measure the audio input duration 开发者_开发知识库in ms .

I want to get to the place where i can get the audio level and write there my own objective c code, or send it to another .m file of my own.

Can someone direct me to that variable that holdes that data ? and what are the things i can erase from it? (dont need openGL,quartz,play sounds,and view any graph ) Thanks a lot.