How can i read the sound data from the microphone? I don't want to record and then access the data, i want to be able to access the sound input live?
You can record sound (PCM samples) from the microphone to very short memory buffers (as short as a few milliseconds in duration). That's as close to "live" as there is using iOS API's. Look at the aurioTouch example for low latency AudioUnit RemoteIO recording code, with live FFT analysis and display.
Check this link:
http://code.google.com/p/ios-coreaudio-example/
Captures from Microphone & plays through speaker.
来源：https://stackoverflow.com/questions/3593247/iphone-how-can-i-read-the-microphone-input