iPhone - How to receive sound/audio when user speaks?

I created an app that plays the song and calculates the decibels of the audio that is being played. Its fine. But I want to make a change in it. That is to receive the sound/audio from outside (when user speaks) and calculate the decibel开发者_开发知识库s. I don't want to record anything. Just receive audio/sound and calculate the decibels? Any hints or tutorials please?

You could try using the source code for one of the sample apps (SpeakHere) in the iOS Developer Library as a starting point: http://developer.apple.com/library/ios/#samplecode/SpeakHere/Introduction/Intro.html

I found the src code "https://github.com/jkells/sc_listener_sample" which is working without any modifications.