Why is the coreaudiod daemon using 5% or more CPU? Every time I listen to music on iTunes or VLC, I notice that the process coreaudiod causes an unusually high CPU usage (5% or more).
Are you having the same issue? What's the reason for such a high CPU usage?

Recent OS X updates have not changed this observation. Restarting (or killing the process so it respawns) doesn't fix the problem. After a couple of seconds, CPU usage of coreaudiod goes above 5% again.

It's important to note that using line out makes the problem go away and coreaudiod's CPU usage goes down to 1%-2%.
The high CPU usage of coreaudiod is due to the ambient noise reduction software working (surprisingly, even when the built-in microphone is not in use).

Go to System Preferences > Sound > Input and uncheck the Use ambient noise reduction box.

Then, either reboot or run this one-liner to reload coreaudiod, and you should see coreaudiod CPU usage drop to 1% or less.