As per the instructions here:
http://developer.apple.com/library/mac/#documentation/MusicAudio/Conceptual/CoreAudioOverview/WhatisCoreAudio/WhatisCoreAudio.html#//apple_ref/doc/uid/TP40003577-CH3-SW1
It says:
The Core Audio SDK assumes you will use Xcode as your development environment.
You can download the latest SDK from http://developer.apple.com/sdk/. After installation, the SDK files are located in /Developer/Examples/CoreAudio.
I looked at all the SDKs and did a search for Core audio. Nothing shows up. Does anyone know where I can find the Core Audio SDKs?
The documentation is out of date. Core Audio SDK is included with current Xcode 4.2. You need to link to it like this:
and of course include its header file.