If this issue occurs, you may see this icon when you press a keyboard volume control key.

Download and install the LED Cinema Display Software Update 1.0.
These Macintosh computers support Mini DisplayPort audio:
- iMac (21.5-inch, Mid 2010)
- iMac (27-inch, Mid 2010)
- MacBook Pro (13-inch, Mid 2010)
- MacBook Pro (15-inch, Mid 2010)
- MacBook Pro (17-inch, Mid 2010)
- MacBook (13-inch, Mid 2010)
- Mac Pro (Mid 2010)
- Mac mini (Mid 2010)