[racket] receive data from microphone, wav file's data chunk value represention

hello

I want to make voice pitch classfying program in scheme

for that,

I want to know

0x1. how wav file's data chunk value represent lowest and highest and mid point

0000 for lowest, FFFF for highest and 8FFF for mid point?

0x2. how to receive data from microphone?

and any advice or suggestion for classyfing voice pitch?

thanks alot!

if my question is vague, unclear, or need fixing, please let me know