audiodisplaymacbook promacosthunderbolt
I have a Dell monitor connected through a thunderbolt port.
Sometimes my Mac for some reason is attempting to play audio through that port. How do I stop this from happening?
It appears in my list of sound outputs in system preferences but I have headphones selected. Unplugging the monitor from the thunderbolt port makes the audio work correctly.
You should be able to use the Audio MIDI Utility (a.k.a. Audio MIDI Setup on Mountain Lion) to create an Aggregate device to mix both output destinations into one item the OS can select.
The Help topics in OSX around this area are...
If you don't have Garageband installed you can also use Quicktime.
File -> New Audio Recording. You will see the following screen:
Built-in Input: Line in as shown in the screenshot.
Best Answer
Same thing happened to me. You have to manually change it in System Preferences > Sound > Output Volume.